Next Stop for Parkinson's Disease Research: Outer Space

Next Stop for Parkinson's Disease Research: Outer Space:

The International Space Station as seen in a photo taken in 2010.

Credit: NASA

In an effort to find new treatments for Parkinson's disease, researchers are sending their experiments to space.

This Monday (Aug. 14), researchers will launch a key Parkinson's disease protein, called LRRK2, to the International Space Station (ISS). The microgravity conditions in space should offer a better test environment for their experiments with this protein, the researchers said.

The materials for their experiments will travel aboard the SpaceX Dragon capsule as part of a mission to send supplies and science experiments to the ISS.

The work is a collaboration between The Michael J. Fox Foundation for Parkinson's Research and the Center for the Advancement of Science in Space (CASIS).

LRRK2 is a type of protein that modifies other proteins. Mutations in the gene that codes for LRRK2 are thought to cause Parkinson's disease in some people. Researchers have hypothesized that developing drugs to inhibit LRRK2, or block its activity, could help prevent Parkinson's or slow its progression. [10 Celebrities with Chronic Illnesses]

But before scientists can develop a drug to inhibit LRRK2, they need to know the precise structure of this protein. One way to get a detailed view of its structure is by growing crystals of LRRK2 in lab dishes. However, on Earth, gravity can interfere with the growth of these crystals, and keep them small.

"The quality of our crystals is just not good enough [on Earth]," Sebastian Mathea, a researcher at the University of Oxford who is involved in the LRRK2 project, said during a news conference about the project Tuesday (Aug. 8).

This is where the ISS research comes in: Researchers hope that the microgravity conditions in space will allow the crystals to grow bigger with fewer defects. The scientists can then get a sharper view of the crystal structure.

Scientists will grow the LRRK2 crystals for about a month in space. Then, the crystals will be sent back to Earth, where they will be analyzed with high-energy X-rays, Mathea said.

Parkinson's disease is a progressive neurological disorder that affects people's movement abilities, and can result in symptoms such as tremors, slowed movements and muscle stiffness. There are currently no treatments to stop or reverse the progression of the disease, according to The Michael J. Fox Foundation.

Original article on Live Science.

Ancient Pueblo Rock Art Depicts a 'Celebratory' Solar Eclipse

Ancient Pueblo Rock Art Depicts a 'Celebratory' Solar Eclipse:

The rock art depicting a solar eclipse, possibly from A.D. 1097, looked "more celebratory than frightening," said a University of Colorado archaeoastronomer.

Credit: J Mckim Malville/University of Colorado

Millions of people will gaze at the Great American Eclipse on Aug. 21, shooting photographs and taking selfies. A thousand years ago, early Pueblo people, called Chacoans, captured their experiences of a total solar eclipse by carving it into a rock — a circle with looping streamers that resemble the sun's outer atmosphere, or corona.

Not only does this rock art, or petroglyph, depict a solar eclipse with a gigantic eruption of plasma called a coronal mass ejection (CME), its looping lines may have evoked a wondrous, inspirational experience, said solar astronomer J. McKim Malville, a University of Colorado Boulder professor emeritus, who is an expert in archaeoastronomy.

"The petroglyph looks more celebratory than frightening," Malville told Live Science. "If our interpretation is correct, they tried to depict the extraordinary sight of the corona, like nothing seen before — associated [it] with a deity that was even more mysterious and powerful than they imagined." [See Photos of the Petroglyph of the Solar Eclipse]

Malville discovered the petroglyph in 1992, while on a scientific excursion into Chaco Canyon, New Mexico, with W. James Judge, then a professor of anthropology at Fort Lewis College in Colorado. They found the petroglyph among others pecked into a large boulder called Piedra del Sol, near the ruins of a cultural hub for the Chacoans, who thrived there between A.D. 900 and 1150.

A petroglyph found in Chaco Canyon in New Mexico depicts a solar eclipse with a huge coronal mass ejection (an eruption of plasma from the sun).

Credit: J Mckim Malville/University of Colorado


When he saw it, Malville immediately recognized something familiar.

"Some people might see it as a bug or a tick or a spider," he said. "But it struck me as very similar to photographs of coronal mass ejections that I'd seen, and drawings."

In 2014, Malville and professor José Vaquero of the University of Extremadura in Cáceres, Spain, published a study in the Journal of Mediterranean Archaeology and Archaeometry describing the discovery. They knew that an eclipse had occurred in the region on July 11, 1097, and that the sun's corona and even CMEs are visible to the naked eye during totality (when the moon's shadow completely blocks the sun's light from reaching Earth). But they needed evidence that the sun was in a period of heightened activity, known as solar maximum, when such ejections are most common. It occurs about every 11 years or so, with some variation in the intensity, Malville said.

He and his colleague consulted several sources to determine the level of activity around the time of the eclipse. They looked at data from ancient tree rings, which store traces of atmospheric carbon from photosynthesis and also provide a natural calendar of annual growth. During periods of high solar activity, the sun's more intense magnetic fields deflect cosmic rays from reaching Earth, reducing the amount of radioactive carbon, found as isotope carbon-14, in tree rings. For the period around 1097, the carbon-14 isotopes were low.

Naked-eye observations of sunspots recorded in ancient Chinese texts also indicated higher solar activity, as did historical data from northern Europeans on the annual number of so-called "auroral nights." The evidence pointed to high levels of activity on the sun during the 1097 eclipse. [The 8 Most Famous Solar Eclipses in History]

"It turns out, the sun was in a period of very high solar activity at that time, consistent with an active corona and CMEs," Malville said in news statement.

The depiction itself, a circle with looping streamers radiating from the edge, struck Malville as something jubilant, not frightening.

There are cultures that consider eclipses as dangerous and fearsome omens during the moments when the day turns into "night," Malville said.

But not all.

He recalled viewing the June 30, 1972, eclipse in Kenya, camped at the eastern edge of Lake Turkana among Turkana, Samburu and El Molo tribes. During the eclipse, the El Molo went into their huts, as they do every evening, remaining there until light returned; they didn't seem influenced at all by the event, he said. But the other tribes came to the campsite to view the eclipse.

This particular event lasted 7 minutes, an unusually long time, and the people there had a chance to see the beauty of the corona during totality.

"The brightness of the corona is about the brightness of the full moon, so it's easily seen with the naked eye," Malville said. (REMEMBER, never look directly at the sun or a solar eclipse without special protective viewers, though you can look at the eclipse without glasses ONLY during the couple of minutes of totality.)

Afterward, the people performed dances to celebrate the eclipse and thank the astronomers for the chance to see it.

Malville thinks that the 1097 eclipse in Chaco Canyon may have stirred a similar sense of wonder in the early Pueblo people. After 1100, the people built 10 large houses, called the Great Houses in Chaco, all of which are in areas that provide dramatic views of the rising or setting sun at the winter or summer solstices, he said.

"There is the possibility that the glory of that experience for the people living in Chaco in 1097 was transformed to an increased reverence for or an increased appreciation of the sun," Malville said.

He has a theory about why some modern people might claim that ancient civilizations were terrified by eclipses.

"They have never seen the full glory of an eclipse themselves," he said.

Originally published on Live Science.

Is Dark Matter Less 'Lumpy' Than Predicted?

Is Dark Matter Less 'Lumpy' Than Predicted?:

Composite picture of stars over the Cerro Tololo Inter-American Observatory in Chile.

Credit: Reidar Hahn/Fermilab

Don Lincoln is a senior scientist at the U.S. Department of Energy's Fermilab, the country's largest Large Hadron Collider research institution. He also writes about science for the public, including his recent "The Large Hadron Collider: The Extraordinary Story of the Higgs Boson and Other Things That Will Blow Your Mind" (Johns Hopkins University Press, 2014). You can follow him on Facebook. Lincoln contributed this article to Live Science's Expert Voices: Op-Ed & Insights.

For as long as we have kept records, humanity has marveled at the night sky. We have looked at the heavens to determine the will of the gods and to wonder about the meaning of it all. The mere 5,000 stars we can see with the unaided eye have been humanity’s companions for millennia.

Modern astronomical facilities have shown us that the universe doesn't consist of just thousands of stars — it consists of hundreds of billions of stars in our galaxy alone, with trillions of galaxies. Observatories have taught us about the birth and evolution of the universe. And, on Aug. 3, a new facility made its first substantive announcement and added to our understanding of the cosmos. It allows us to see the unseeable, and it showed that the distribution of matter in the universe differed a bit from expectations.

The Dark Energy Survey (DES) is a collaboration of about 400 scientists who have embarked on a five-year mission to study distant galaxies to answer questions about the history of the universe. It uses the Dark Energy Camera (DEC) attached to the Victor M. Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatoryin the Chilean Andes. DEC was assembled in the U.S. at Fermilab near Batavia, Illinois, and is a 570-megapixel camera able to image galaxies so far away that their light is a millionth as bright as the dimmest visible stars.

Dark energy and dark matter

DES is hunting for dark energy, which is a proposed energy field in the universe that is a repulsive form of gravity. While gravity exerts an irresistible attraction, dark energy pushes the universe to expand at an ever-increasing rate. Its effect was first observed in 1998, and we still have many questions about its nature.

However, by measuring the location and distance of 300 million galaxies in the southern night sky, the survey will be able to make important statements about another astronomical mystery, called dark matter. Dark matter is thought to be five times more prevalent in the universe than ordinary matter. Yet it doesn’t interact with light, radio waves or any form of electromagnetic energy. And it doesn’t appear to congregate to form large bodies like planets and stars.

Map of dark matter made from gravitational lensing measurements of 26 million galaxies in the Dark Energy Survey.

Credit: Chihway Chang of the Kavli Institute for Cosmological Physics at the University of Chicago and the DES collaboration


There is no way to directly see dark matter (hence the name). However, its effects can be seen indirectly by analyzing how fast galaxies rotate. If you calculate the rotational speeds supported by the galaxies’ visible mass, you will discover that they rotate more quickly than they should. By all rights, these galaxies should be torn apart. After decades of research, astronomers have concluded that each galaxy contains dark matter, which generates the additional gravity that holds the galaxies together. [6 Weird Facts About Gravity]

Dark matter in the universe

However, on the much larger scale of the universe, studying individual galaxies is not sufficient. Another approach is needed. For that, astronomers must employ a technique called gravitational lensing.

Gravitational lensing was predicted in 1916 by Albert Einstein and was first observed by Sir Arthur Eddington in 1919. Einstein’s theory of general relativity says that the gravity that we experience is really caused by the curvature of space-time. Since light travels in a straight line through space, if space-time is curved, it will look to an observer as if light were travelling a curved path through space. [8 Ways You Can See Einstein's Theory of Relativity in Real Life]

This phenomenon can be harnessed to study the amount and distribution of dark matter in the universe. Scientists who peer at a distant galaxy (called the lensing galaxy), which has another galaxy even farther away behind it (called the observed galaxy), can see a distorted image of the observed galaxy. The distortion is related to the mass of the lensing galaxy. Because the mass of the lensing galaxy is a combination of visible matter and dark matter, gravitational lensing allows scientists to directly observe the existence and distribution of dark matter on scales as large as the universe itself.  This technique also works when a large cluster of foreground galaxies distorts the images of clusters of even more distant galaxies, which is the technique employed for this measurement.

Lumpy or not?

The DES collaboration recently released an analysis using exactly this technique. The team looked at a sample of 26 million galaxies at four different distances from Earth. The closer galaxies lensed ones that were farther away. By using this technique and looking carefully at the distortion of the images of all of the galaxies, they were able to map out the distribution of invisible dark matter and how it moved and clumped over the past 7 billion years, or half the lifespan of the universe.

As expected, they found that the dark matter of the universe was "lumpy." However, there was a surprise — it was a little less lumpy than previous measurements had predicted.

One of these contradictory measurements comes from the remnant radio signal from the earliest time after the Big Bang, called the cosmic microwave background (CMB). The CMB contains within it the distribution of energy in the cosmos when it was 380,000 years old. In 1998, the Cosmic Background Explorer (COBE) collaboration announced that the CMB was not perfectly uniform, but rather had hot and cold spots that differed from uniform by 1 part in 100,000. The Wilkinson Microwave Anisotropy Probe (WMAP) and Planck satellites confirmed and refined the COBE measurements.

Over the 7 billion years between when the CMB was emitted and the time period studied by DES, those hotter regions of the universe seeded the formation of structure of the cosmos. Nonuniform energy distribution captured in the CMB, combined with the amplifying force of gravity, caused some spots in the universe to become denser and others less so. The result is the universe we see around us.

The CMB predicts the distribution of dark matter for a simple reason: The distribution of matter in our universe in the present depends on its distribution in the past. After all, if there were a clump of matter in the past, that matter would attract nearby matter and the clump would grow. Similarly, if we were to project into the distant future, the distribution of matter today would affect tomorrow's for the same reason.

So, scientists have used measurements of the CMB at 380,000 years after the Big Bang to calculate what the universe should look like 7 billion years later. When they compared the predictions to the measurements from DES, they found that the DES measurements were a little less lumpy than the predictions.

Incomplete picture

Is that a big deal? Maybe. The uncertainty, or error, in the two measurements is big enough that it means they don’t disagree in a statistically significant way. What that simply means is that no one can be sure that the two measurements really disagree. It could be that the discrepancies arise by chance from statistical fluctuations in the data or small instrumental effects that were not considered.

Even the study’s authors would suggest caution here. The DES measurements have not yet been peer-reviewed. The papers were submitted for publication and the results were presented at conferences, but firm conclusions should wait until the referee reports come in.

So, what is the future? DES has a five-year mission, of which four years of data have been recorded. The recently announced result uses only the first year’s worth of data. More recent data is still being analyzed. Further, the full data set will cover 5,000 square degrees of the sky, while the recent result only covers 1,500 square degrees and peers only half of the way back in time. Thus, the story is clearly not complete. An analysis of the full data set won’t be expected until perhaps 2020.

Yet, the data taken today already could mean that there is a possible tension in our understanding of the evolution of the universe. And, even if that tension disappears as more data is analyzed, the DES collaboration is continuing to make other measurements. Remember that the letters "DE" in the name stand for dark energy. This group will eventually be able to tell us something about the behavior of dark energy in the past and what we can expect to see in the future. This recent measurement is just the very beginning of what is expected to be a scientifically fascinating time.

Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google+. The views expressed are those of the author and do not necessarily reflect the views of the publisher.

This version of the article was originally published on Live Science.

Summer Triangle: Asterism of 3 Stars From 3 Constellations

Summer Triangle: Asterism of 3 Stars From 3 Constellations:

In this image we can see the asterism of the "Summer Triangle" a giant triangle in the sky composed of the three bright stars Vega (top left), Altair (lower middle) and Deneb (far left).

Credit: A. Fujii

The Summer Triangle is a Northern Hemisphere asterism (stars of similar brightness recognized in a distinctive shape). Unlike many other asterisms, the Summer Triangle is actually an amalgamation of stars from three separate constellations.

Three stars make up the triangle: Deneb, Vega and Altair. Deneb is the farthest away from Earth among these three, and is the brightest star in the constellation Cygnus; it forms the tail of the Swan. Coincidentally, Deneb is also the head of another asterism known as the Northern Cross, which is contained in Cygnus.

Vega is the brightest star of an otherwise dim and small constellation, Lyra (the Harp). Vega is one of the brightest stars in the night sky. (Sirius is the brightest in the night sky, but appears in the winter of the Northern Hemisphere.) About 12,000 years ago, it used to be the North Star due to an effect called precession, where the Earth's north-pointing direction changes due to a wobbling axis.

Rounding out the asterism is Altair, which is the brightest star in the constellation Aquilia (the Eagle.) Altair is one of the brightest close stars to Earth.

Asterism popularized in the 1950s

Unlike other asterisms such as the Big Dipper or the Little Dipper, the Summer Triangle is a recently popularized term.

The three stars have been recognized for some time as having similar brightness (although it should be noted that Deneb is about 1,400 light-years away while Vega and Altair are roughly 20 light-years away each, showing how much more luminous Deneb is.) [Related: Brightest Stars: Luminosity & Magnitude]

“It's appeared in various works for generations,” said Tom Kerss, an astronomer at the Royal Observatory Greenwich, in a Space.com interview. “Johann Bode traced the Summer Triangle in his star maps to the early 19th century, but it was unlabelled. It was then recognized as a way of navigating.”

A rough approximation of the term appears in works by Oswald Thomas, an Austrian astronomer, who referred to it as “Sommerliches Dreieck” (the Summerly Triangle) in the 1930s, Kerss added. Then in the 1950s, two astronomy popularizers picked up the term and made it generally known in the public: H.A. Rey in the United States and Patrick Moore in the United Kingdom.

Lie back on a warm summer night and look straight up. You’ll see three bright stars: Vega, Deneb, and Altair. These mark the corners of the “Summer Triangle” and are your guides to the three constellations of Lyra, Cygnus, and Aquila.

Credit: Starry Night Software

Recent astronomical news

Vega was discovered to have an asteroid belt in 2013, leading astronomers to suggest that the star could host planets. Astronomers detected signs of icy asteroids in the outer regions of the star, and space rocks closer in. It was a similar signature to what was detected in another bright star in the sky, that of Fomalhaut.

"Overall, the large gap between the warm and the cold belts is a signpost that points to multiple planets likely orbiting around Vega and Fomalhaut," said Kate Su, an astronomer at the Steward Observatory at the University of Arizona, at the American Astronomical Society 2013 annual meeting.

Vega is also a fast rotater. In 2006, astronomers discovered it is whirling around so quickly — every 12.5 hours — that its equator is many thousand degrees cooler than its poles. If the star rotated just 10 percentage points faster, it would be at its critical rotation speed — the point at which the star would self-destruct due to its fast rotation. The star is sometimes cited in the literature as a comparison to the rotation of other stars, such as the slowly rotating KIC 11145123.

Altair also rotates fairly quickly and has flattening at its poles, which astronomers spotted in 2006 using long-baseline interferometery (which links together numerous telescopes to together look at a region of the sky.) In 2014, the XMM-Newton mission observed Altair, showing that the star has a corona (outer atmosphere) that changes depending on magnetic and rotational activity.

Deneb, meanwhile, is on astronomers' watchlist as a probable future supernova. Because the star is so bright, it is sometimes used as a testing platform for new professional telescopes, or for simulating the positions of objects in astronomical pictures.

Additional resources

• The Stars website, created by Jim Kaler, professor emeritus of astronomy at the University of Illinois, has more information about the Summer Triangle.
• NASA's "Astronomy Picture of the Day" features a beautiful image of the Summer Triangle over Catalonia.
• Astronomer David Darling's Encyclopedia of Science has an entry on the Summer Triangle.

Solar Eclipses Through the Ages: From (Possible) Beheadings to Science

Solar Eclipses Through the Ages: From (Possible) Beheadings to Science:

Through the ages, people have documented total solar eclipses. Here, an artistic depiction of the July 29, 1878 total solar eclipse by E.L. Trouvelot.

Credit: New York Public Library

Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI Science Center. Sutter leads science-themed tours around the world at AstroTouring.com. Sutter contributed this article to Space.com's Expert Voices: Op-Ed & Insights.

People enjoy looking at the sky. People enjoy writing down minute details of their daily lives. Ergo, when people see something interesting in the sky, they write it down. We have historic — and surprisingly, prehistoric — records of celestial events going back thousands of years, including solar eclipses. So when you pick just the right Instagram filter for your "solar selfie" this Aug. 21, you're following in the footsteps of an ancient and noble tradition. (Note: Do not photograph an eclipse without a safe solar filter when any portion of the sun is visible.)

Due to their very nature, prehistoric records of solar eclipses are the hardest to interpret. Does that swirly thing represent the sun? Are the concentric circles the full moon? The new moon? And what about those zigzags? If we're correctly interpreting the petroglyphs on the ancient monuments near Loughcrew, Ireland, then the oldest recorded solar eclipse dates to 3340 B.C.

Once we enter written history things get a little more reliable. A peculiar tale comes down to us telling the story of Chinese Emperor Chung K'ang, who apparently beheaded his court astronomers for failing to predict the eclipse of 2137 B.C. While the anecdote may be purely apocryphal, it is a good way to frighten young astronomers around the campfire.  [Total Solar Eclipse 2017: When, Where and How to See It (Safely)]

I should mention that the Chinese went on to record nearly a thousand eclipses from the eighth century B.C. until the fifth century B.C., with no associated beheadings reported.

They weren't alone, however. The Babylonians and Greeks busied themselves recording solar eclipses, using colorful language like "the sun was put to shame," as one ancient clay tablet attests. Solar eclipses were too hard to predict with any degree of confidence with the limited accuracy available to the ancients — poor consolation to the Chinese court astronomers, I know — but as far as we can tell, all the civilizations that kept track of eclipses quickly realized that they were a result of the natural motions of the sun and moon.

That said, the astrological worldview posited that the motions of the heavens were connected to earthly events, so solar eclipses weren't necessarily to be feared (at least, by the intelligentsia of their respective cultures), but were used to read the fortunes of emperors, generals, religious leaders and other important folk. [10 Solar Eclipses That Changed Science]

Entering the scientific era of astronomy, solar eclipses began to be used for more than just finding a tenuous connection to the fortunes of the big boss. Observers began to study the corona in more detail, discovering helium (Helios, like the Greek god of the sun — get the name now?) in the process. Later on, they would be used to verify the prediction of general relativity that massive objects can bend the path of light.

These days, as on Aug. 21, they will be an opportunity to ooh and ah at the beauty of the natural world while simultaneously doing research. And no beheadings.

Follow Paul @PaulMattSutter and facebook.com/PaulMattSutter. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

The Mars Colony of the Future Could Be Powered by This Advanced Microgrid

The Mars Colony of the Future Could Be Powered by This Advanced Microgrid:

Credit: 3quarks

SpaceX and Tesla CEO Elon Musk wants to put a million people on Mars in the next century. They'll be ferried to the Red Planet on a fleet of spaceships that can each carry 100 or more people, and make their living in an environment bereft of oxygen and full of danger.

While you can't breathe the air on Mars, with some creative thinking you could bring in many of the comforts of home. Mars has great potential for energy generation. While its atmosphere is dusty, the sun's light reaches down to the surface, allowing for solar panels. And the wind that provides the driving force of erosion on Mars could be harnessed for wind farms.

The industrial manufacturing giant Siemens is trying to plan for this reality.

"Mars will be the ultimate microgrid," the company says on its website. "With no centralized power sources, communities will one day rely on decentralized energy systems."

Their first major test case: an indigenous reservation about 5.5 hours north of San Francisco. The Blue Lake Rancheria is home to the Aboriginal Wiyot, encompassing members of the Wiyot, Yurok, Tolowa, and Cherokee tribes. It's a 91-acre area, with 53 members living among coastal mountains and large redwood trees.

While the area is rich in natural resources — unlike Mars — the Wiyot have endured regular interruptions with the Pacific Gas & Electric power grid in recent years. That's where Siemens stepped in.

"They got the idea that they wanted to do something about it, and their No. 1 objective was improve reliability, and… to reduce the carbon footprint," said Clark Wiedetz, director of microgrid and renewable integration at Siemens Energy Management.

The result is a microgrid, completed in April, that is expected to save the community more than $200,000 a year. It includes a 500-kilowatt array of solar panels that were designed and built by REC Solar, a Tesla battery storage system, and contributions from other partners. Siemens maintains the microgrid through a computer-operated management system that decides where best to allocate power resources.

"They have the ability to replace what power they take from the grid, when that makes sense or when it's down," Wiedetz said.

The Siemens system makes decisions about where to put the power, basing its analysis on historical data. If a storm were to knock out the power, for example, the microgrid would predict how much power is needed for the Red Cross shelter on site, and allocate resources accordingly.

"A colony on Mars may one day be powered by the types of on-site systems that are already hard at work on Earth," the company says.

Though a similar system could be the answer to sustaining power on Mars, it's hard to know right now what a Martian equivalent would need.

"We don't know what variables to work in the equation," Wiedetz explained. But he said the microgrid system does have some advantages. One big one is that it doesn't rely on cloud computing, which would likely not be in place on Mars. The Wiyot residents can also take on maintenance themselves, with remote assistance — just as astronauts would be expected to do so in deep space.

The microgrid system is adapted from previous software used for utility companies for energy management. It's a new use for the 20-year-old technology, and Wiedetz said Siemens is looking at other ways to implement it, but they're not yet ready to reveal where they plan to do so.

Tesla, which has positioned itself as a major player in battery development, has worked on other microgrids before. In 2016, the company announced that it and its subsidiary SolarCity helped the entire island of Ta’u in American Samoa. Thanks to a newly installed microgrid with solar panels and Tesla batteries, the island (which used to burn 100,000 gallons of fuel a year) could have full power for three days — even when it's cloudy.

Originally published on Seeker.

Solar Eclipse Photography Is About Trial and Error, Says This Astro-Pro

Solar Eclipse Photography Is About Trial and Error, Says This Astro-Pro:

The progression of the 2015 total solar eclipse, imaged from Svalbard, Norway, by astrophotographer Kevin Morefield.

Credit: Kevin Morefield

When Kevin Morefield was young, he wanted to be a sports or nature photographer.

"I wanted to work for Sports Illustrated or National Geographic," he told Space.com. "But only like, 20 people in the world have those jobs, so I got into finance instead."

That day job allowed him to pursue astrophotography as a hobby. Now retired, his photographs have appeared in magazines like Sky and Telescope and the Atlantic, and have won him multiple "Image of the Day" awards from various online outlets. His Instagram feed shows some of his work on deep-sky objects (nebulae, galaxies and the like), planets and eclipse shots. [Total Solar Eclipse 2017: When, Where and How to See It (Safely)]

Morefield said learning to get good shots of an eclipse involves a certain amount of trial and error. During one eclipse, he taped solar filters to his camera lens for the partial eclipse and then pulled them off at the start of totality (when the moon fully covers the disk of the sun).

Kevin Morefield learned how to photograph astronomical objects in his spare time, through lots of trial and error. Morefield pictures here with an automated telescope, which he can operate with his phone or PC, that he uses to capture night-sky images

Credit: Kevin Morefield


"When it came time to take the filters off, I pulled [the camera] out of focus," he said. Morefield had set up an automated system to snap photos during totality, so he didn’t look through the lens and didn't realize his mistake until it was too late. The images were lost, but Morefield said he also had a video camera running. [Best Gear for Taking Photos of the Solar Eclipse]

"I thought I had it on video and I ran back the tape — in 2010, HD digital video still shot on tape — and I saw I had it," he said. "Then the mayor wants to come up and talk and I took video of that and I [later] found I'd taped over it."

One tip Morefield offers for people photographing eclipses: Make sure the camera is in focus during the partial phases. Shoot through a solar filter — otherwise the sunlight will just wash out the picture (and potentially damage your equipment and eyes) — and focus on the edges of the sun. He added that making sure the exposure time is set appropriately is also key, because catching the relatively dim corona (the sun's outer atmosphere) during totality will require different settings than a filtered shot of the partial phase. Lastly, a tracking mount — one that follows the sun across the sky — is essential for close-in shots of the sun.

A two panel mosaic of the Orion Nebula (M42) on the right and the Running Man Nebula (sh2-279) on the left, taken by astrophotographer Kevin Morefield. The image required a total of 18 hours of exposures.

Credit: Kevin Morefield


Automation is also helpful, Morefield said. He currently uses a Canon 6D and generally shoots pictures at an ISO, or "film speed," of 400. The camera also allows for pre-programming sequences of shots with varying exposure times and apertures (not every model of digital SLR has that feature).  [How to Film or Photograph the 2017 Solar Eclipse Like a Pro]

When watching an eclipse — especially a total solar eclipse — most experts recommend focusing on what's happening in the sky rather than fiddling with a camera. On his earlier eclipse shoots, Morefield used a remote shutter release and a tracking mount for that reason.

"[Photography] is not distracting, but I automate a lot," he said. There are even programs that one can download specifically for eclipse photography, such as Eclipse Orchestrator. (For his part, Morefield will be running a program that takes hundreds of images.)

At the same time, Morefield said it's important to think through what you want to accomplish with an eclipse photograph. While it's possible to take close-ups of the sun to capture the corona or other eclipse-related phenomena, it's also not a bad idea to use a wide-angle lens to capture what's happening around you. [The Best 2017 Solar Eclipse Live Video Streams ]

"You might try to get what's going on with people and the sky and the ground," Morefield said. "Like, the diffraction pattern you see on the ground that lasts 3 or 4 seconds. With a superwide angle, you're more likely to see the shadow bands. Or, one could look for projected images of the eclipse made by ordinary objects. A straw hat or leafy tree, for instance, produces dozens of tiny, projected images that can create interesting shots."

When photographing cosmic events, should sometimes it's good to focus on the ground as well as the sky, said astrophotographer Kevin Morefield. Shown here, a shot by Morefield of the northern lights over Svalbard, Norway, in 2015, and a crowd of skywatchers viewing the light show.

Credit: Kevin Morefield


Morefield outlined how he will be taking his pictures during the Aug. 21 total solar eclipse. His program, he said, starts about a minute before first contact (when the moon begins to overlap the sun). About half of the pictures will be taken during totality, which will last for just over 2.5 minutes in his viewing location. The exposure times will range from 1/1600 of a second to 2 seconds.

Before he takes off the solar filter, he will check the camera's focus. Before totality, Morefield says he typically uses a 1/1600 speed and f/8 aperture setting. He pulls off his solar filter when the "Baily's beads" and "diamond ring" effects appear: these are the last spots of light visible on the edge of the moon before the sun's disk is fully hidden.

During the diamond ring phase, Morefield said the corona begins to become visible. He said he uses "bracketed exposure" while imaging the diamond ring, which means taking several pictures at different shutter speeds.

"I'll use a combination of three or so exposures in the diamond ring phase, with exposures also at 1/25 to 1/800," he said. For "Baily's beads, he uses1/4000 to 1/8000" exposure times.

His first exposures of totality will be short, and they will get longer with each shot.

A "diamond ring," which occurs seconds before or after totality during a total solar eclipse, captured by Kevin Morefield.

Credit: Kevin Morefield


Morefield's adventures with eclipse photography started in 2002, but his interest was piqued before that. He grew up looking at the sky through his home telescope and saw a partial solar eclipse over his home in the 1970s. Amazed by pictures of total solar eclipses, seeing one in person became like a "holy grail." He finally planned a trip with his father to see the total solar eclipse over Australia in 2002.

"We had to fly 24 hours to get to Adelaide to drive on the wrong side of the road," Morefield said of the trip. "When we got there, it was with a group of like 1,500 other people … from all over the world."

Seeing a total solar eclipse with such an international group was "a little bit like the Olympics, where people put aside all their differences," Morefield said. "Totality was 27 seconds long and the minute it was over, everybody's like, 'It was worth it.' It's really an emotional experience."

Follow Jesse Emspak on Twitter @Mad_Science_Guy. Follow us @Spacedotcom. We're also on Facebook & Google+. Original story on Space.com. 

Eclipses Were Regarded As Omens in the Ancient World

Eclipses Were Regarded As Omens in the Ancient World:

A solar eclipse observed over Grand Canyon National Park in May 2012.

Credit: Grand Canyon National Park

This article was originally published at The Conversation. The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.

On Monday, Aug. 21, people living in the continental United States will be able to see a total solar eclipse.

Humans have been alternatively amused, puzzled, bewildered and sometimes even terrified at the sight of this celestial phenomenon. A range of social and cultural reactions accompanies the observation of an eclipse. In ancient Mesopotamia (roughly modern Iraq), eclipses were in fact regarded as omens, as signs of things to come.

Solar and lunar eclipses

For an eclipse to take place, three celestial bodies must find themselves in a straight line within their elliptic orbits. This is called a syzygy, from the Greek word "súzugos," meaning yoked or paired.

Solar lunar eclipse diagram.

Credit: Tomruen (Own work)/Wikimedia Commons, CC BY-SA


From our viewpoint on Earth, there are two kinds of eclipses: solar and lunar. In a solar eclipse, the moon passes in between the sun and Earth, which results in blocking our view of the sun. In a lunar eclipse, it is the moon that crosses through the shadow of the Earth. A solar eclipse can completely block our view of the sun, but it is usually a brief event and can be observed only in certain areas of the Earth's surface; what can be viewed as a total eclipse in one's hometown may just be a partial eclipse a few hundred miles away.

By contrast, a lunar eclipse can be viewed throughout an entire hemisphere of the Earth: the half of the surface of the planet that happens to be on the night side at the time.

Eclipses as omens

More than two thousand years ago, the Babylonians were able to calculate that there were 38 possible eclipses or syzygys within a period of 223 months: that is, about 18 years. This period of 223 months is called a Saros cycle by modern astronomers, and a sequence of eclipses separated by a Saros cycle constitutes a Saros series.

Although scientists now know that the number of lunar and solar eclipses is not exactly the same in every Saros series, one cannot underplay the achievement of Babylonian scholars in understanding this astronomical phenomenon. Their realization of this cycle eventually allowed them to predict the occurrence of an eclipse.

The level of astronomical knowledge achieved in ancient Babylonia (southern Mesopotamia) cannot be separated from the astrological tradition that regarded eclipses as omens: Astronomy and astrology were then two sides of the same coin.

Rituals to preempt royal fate

According to Babylonian scholars, eclipses could foretell the death of the king. The conditions for an omen to be considered as such were not simple. For instance, according to a famous astronomical work known by its initial words, "Enūma Anu Enlil" – "When (the gods) Anu and Enlil" – if Jupiter was visible during the eclipse, the king was safe. Lunar eclipses seem to have been of particular concern for the well-being and survival of the king.

In order to preempt the monarch's fate, a mechanism was devised: the "substitute king ritual," or "šar pūhi." There are over 30 mentions of this ritual in various letters from Assyria (northern Mesopotamia), dating to the first millennium B.C. Earlier references to a similar late chronicle, a king of the city of Isin (modern Išān Bahrīyāt, about 125 miles to the southeast of Baghdad), Erra-imitti, was replaced by a gardener called Enlil-bani as part of a substitute king ritual. Luckily for this gardener, the real king died while eating hot soup, so the gardener remained on the throne and became king for good.

The fact is that these two kings, Erra-imitti and Enlil-bani, did exist and reigned successively in Isin during the 19th century B.C. The story, however, as told in the late "Chronicle of Early Kings," bears all the trademarks of a legend. The story was probably devised to explain a dynastic switch, in which the royal office passed from one family or lineage to another, instead of following the usual father-son line of succession.

Looking for meaning in the skies

A lunar eclipse.

Credit: Neil Saunders, CC BY-NC-ND


Mesopotamia was not unique in this regard. For instance, a chronicle of early China known as the "Bamboo Annals" (竹書紀年 Zhúshū Jìnián) refers to a total lunar eclipse that took place in 1059 B.C., during the reign of the last king of the Shang dynasty. This eclipse was regarded as a sign by a vassal king, Wen of the Zhou dynasty, to challenge his Shang overlord.

In the later account contained in the "Bamboo Annals," an eclipse would have triggered the political and military events that marked the transition from the Shang to the Zhou dynasty in ancient China. As in the case of the Babylonian "Chronicle of Early Kings," the "Bamboo Annals" are a history of earlier periods compiled at a later time. The "Bamboo Annals" were allegedly found in a tomb about A.D. 280, but they purport to date to the reign of the King Xiang of Wei, who died in 296 B.C.

The complexity of human events is rarely constrained and determined by one single factor. Nevertheless, whether in ancient Mesopotamia or in early China, eclipses and other omens provided contemporary justifications, or after-the-fact explanations, for an entangled set of variables that decided a specific course of history.

Even if they mix astronomy and astrology, or history with legend, humans have been preoccupied with the inescapable anomaly embodied by an eclipse for as long as they have looked at the sky.

Gonzalo Rubio, Associate Professor of Classics & Ancient Mediterranean Studies, History, and Asian Studies, Pennsylvania State University

This article was originally published on The Conversation. Read the original article. Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. 

Solar Eclipse 2017: What You Can (and Can't) See in New York City

Solar Eclipse 2017: What You Can (and Can't) See in New York City:

A partial solar eclipse is seen just after sunrise over the Queens borough of New York across the East River on Nov. 3, 2013.

Credit: Stan Honda/AFP/Getty

NEW YORK — New York City isn't in the "path of totality," but millions of New Yorkers will be able to see a partial solar eclipse on Aug. 21 — and it's totally worth checking out, local astrophysicist and science celebrity Neil deGrasse Tyson said yesterday (Aug. 14) in a briefing at the American Museum of Natural History (AMNH).

Skywatchers along a narrow path from Oregon to South Carolina will see skies darken during the total solar eclipse. But the rest of the U.S. will still have a pretty cool view of this astronomical event using solar eclipse glasses or some type of pinhole projector.

In New York City, the partial eclipse will begin at 1:23 p.m. local time, when the moon first appears to touch the sun in the sky. "It starts to look like the Death Star is moving in front of the sun," Jackie Faherty, senior scientist and education manager at AMNH, said during the briefing. The museum will host an eclipse-watching event. [Amazing Solar Eclipse Pictures from Around the World]

By 2:44 p.m., the moon will block about 72 percent of the sun's surface as the partial eclipse reaches its maximum. Then, the cusps of the crescent-shaped sun will appear to be pointing downward, Joe Rao, FiOS1 meteorologist and Space.com columnist, said during the briefing. After the maximum eclipse, the moon will slowly begin to slide off the sun's face, and the eclipse will end at 4 p.m.

Although the skies won't darken beneath a partial eclipse in the same way that total solar eclipses briefly turn day into night, those who are paying attention may still notice some environmental changes during the partial eclipse, Rao said. He quoted American astronomer Leslie Peltier, who described his experience while watching a 75 percent partial eclipse in Delphos, Ohio, in 1918:

"At mid-eclipse, I turned away and looked about. Everything I saw — the nearby fields, the distant vistas — all seemed wrapped in some strange, unearthly early twilight. The sky seemed darker, shadows sharp and distinct. A cool wind — almost chilly — had sprung up from the West."

The partial eclipse over New York on Aug. 21 will have about the same magnitude as Peltier's partial eclipse and should bring a similar experience, Rao said. "If we're lucky enough to have clear weather here in New York at 2:44 next Monday afternoon, I have a feeling that's pretty much what we're going to see in the New York metropolitan area."

Rao equated a partial solar eclipse to a flashlight with low batteries. While the light still shines, it's not as bright as a flashlight with full batteries, and the light looks "almost yellowish" in color. "That's kind of like what it will be like next week at the midpoint of the eclipse," he said. "There's going to be a certain amount of yellowness in the air along with that dimming or diminishing twilight for a few minutes around the peak."

So, if you're in the city around the peak of the partial eclipse, don't forget to step outside and check it out. Solar eclipse glasses are the best way to see the partial eclipse, and you can still find them in stores around the city. AMNH will provide safe viewing glasses to visitors at the Hayden Planetarium's special event. But if you can't get the glasses in time and can't make it to the museum, Tyson has a great alternative that most New Yorkers can find in their own homes.

"Go into your kitchen and get a spaghetti strainer or a colander," Tyson said. "Not with mesh, the kind with holes in it. Go outside and hold that up over the ground. Each one of those holes will act as a pinhole camera and you'll see hundreds of images of the crescent sun on the ground and you can watch the eclipse unfold safely…that's the urban version of watching the pinhole camera images through the modeled light of sunlight passing through the leaves of a tree. It'll just be fun." So if you happen to be near any tree during the partial eclipse, check out their shadows and look for the tiny eclipse projections on the ground.

There's really no excuse for missing out on this celestial event, whether you're lucky enough to be in the path of totality, or if only a partial solar eclipse is heading your way. "It won't happen that often in your lifetime that you can walk outside of your own house and watch even a partial happen," Faherty said. The next time any type of solar eclipse will be visible over New York will be during a partial annular eclipse in 2021.

Editor's note: Find out how the solar eclipse will look from your location — Space.com has teamed up with Simulation Curriculum to offer this awesome Eclipse Safari app to help you enjoy your eclipse experience. The free app is available for Apple and Android, and you can view it on the web. If you take an amazing photo of the Aug. 21 solar eclipse, let us know! Send photos and comments to spacephotos@space.com.

Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

Opportunity: Longest-Running Mars Rover

Opportunity: Longest-Running Mars Rover:

NASA's Mars Exploration Rover Opportunity used its panoramic camera (Pancam) during the mission's sols 1282 and 1284 (Sept. 2 and Sept. 4, 2007) to take the images combined into this mosaic view of the rover. The downward-looking view omits the mast on which the camera is mounted. Image released Feb. 17, 2012.

Credit: NASA/JPL-Caltech/Cornell

Opportunity is a rover that has been working on Mars since January 2004. Originally intended to last 90 days, the machine is still trekking after 13 years on the Red Planet. In 2015, it passed a driving milestone, reaching more than a marathon's worth of distance (26.2 miles, or 42.1 kilometers) – and the rover keeps racking up driving time.

Lately, however, it has been showing its age. In 2014 and early 2015, NASA made several attempts to restore Opportunity's flash memory capabilities after the rover experienced problems. Flash memory allows the rover to store information even when it is powered off. In 2015, NASA decided to continue most operations with random-access memory instead, which keeps data only when the power in the rover is on. At the time, NASA said the only change to operations will be requiring Opportunity to send high-priority data right away, as it cannot be stored if the rover is turned off.

That said, the mission has been extremely productive on the Red Planet. Opportunity has explored two large craters — Victoria and Endeavour — among many other locations. Along the way, the rover has found multiple signs of water — while surviving a sand trap and bad dust storm.

Making an orphan's dream come true

Opportunity and its twin rover, Spirit, received their names from 9-year-old Sofi Collis. She was the winner of a naming contest NASA held (with assistance from the Planetary Society and sponsorship from Lego) to find monikers for the Mars Exploration Rovers. Siberian-born Collis was adopted at age 2 and came to live with her new family in Scottsdale, Arizona.

"I used to live in an orphanage," Collis wrote in her winning essay. "It was dark and cold and lonely. At night, I looked up at the sparkly sky and felt better. I dreamed I could fly there. In America, I can make all my dreams come true. Thank you for the 'Spirit' and the 'Opportunity.'"

The Mars Exploration Rovers launched in 2003 on a 283-million-mile (455.4 million kilometers) journey to hunt for water on Mars. The $800-million cost for the two of them covered a suite of science instruments. Site survey tools included a panoramic camera, as well as a mini-thermal emission spectrometer that was supposed to search for signs of heat. Each rover also had a small arm with tools such as spectrometers and a microscopic imager.

Cruise to Mars

Opportunity left Earth July 7, 2003, aboard a Delta II rocket en route to a landing site at the Martian equator called Meridiani Planum. NASA was intrigued by a layer of hematite that the orbiting Mars Global Surveyor spotted from above. As hematite (an iron oxide) often forms in a spot that had liquid water, NASA was curious about how the water got there in the first place and where the water went.

The 384-pound rover made its final approach to Mars on Jan. 25, 2004. It plowed through the Martian atmosphere, popped out a parachute and then vaulted to the surface in a cocoon of airbags.

Opportunity rolled to a stop inside a shallow crater just 66 feet (20 meters) across, delighting scientists as the first pictures beamed back from the Red Planet. "We have scored a 300-million mile interplanetary hole-in-one," quipped Cornell University's Steve Squyres, principal investigator for the rover's science instruments, in a press release in the days after the landing.

Early sols of science

Opportunity and Spirit (which had landed successfully three weeks earlier, on Jan. 3, 2004) had a primary goal to "follow the water" during their time on Mars. They would hunt for any environments that showed evidence of water activity, particularly looking for minerals that may have been left behind after water came through.

Both rovers met that goal quickly. In early March, just six weeks after landing, Opportunity identified a rock outcrop that showed evidence of a liquid past. The rocks at "Guadalupe" had sulfates as well as crystals inside of niches, which are both signs of water. Spirit found water evidence of its own that same week.

Two weeks later, Opportunity found hematite inside some small spheres that NASA dubbed "blueberries" because of their size and shape. Using a spectrometer, Opportunity found evidence of iron inside a group of berries when comparing it to the bare, underlying rock.

The month wasn't yet over when Opportunity discovered more evidence of water, this time from images of a rock outcrop that probably formed from a deposit of saltwater in the ancient past. Chlorine and bromine found in the rocks helped solidify the theory.

It was a positive start to Opportunity's mission — and it hadn't even left the crater where it had landed yet. Before Opportunity's 90-day prime mission was over, the golf-cart size rover clambered out of Eagle Crater and ventured to its next science target about half a mile away: Endurance Crater. It spotted more water signs there in October.

Stuck in the sand

One of Opportunity's most dangerous moments came in 2005, when the rover was mired in the sand for five weeks. NASA had put the rover into a "blind drive" on April 26, 2005, meaning the rover was not checking for obstacles as it went. Opportunity then plowed into a 12-inch-high (30 cm) sand dune, where the six-wheeled rover initially had trouble getting out.

To save the stranded rover, NASA ran tests on a model of the rover in a simulated Martian "sandbox" at the Jet Propulsion Laboratory. Based on what they learned in the sandbox, the rover drivers then sent a series of commands to Opportunity. It took the rover about 629 feet (191 meters) of wheel rotations before it was able to move forward three feet, but it cut itself free in early June 2005.

NASA chose to move the rover forward in more careful increments, which was especially important because Opportunity lost the full use of its right-front wheel (because of a seized steering motor) just days before it got stuck in the sand. The rover could still move around just fine with its other three steerable wheels, NASA said.

Opportunity's experience in the sand came in handy in October 2005, when NASA detected unusual traction problems on Sol 603. Just 16 feet into a planned 148-foot drive, a slip check system on board automatically stopped the rover when it went past a programmed limit. Two Martian days later, Opportunity backed itself out of the problem and kept on going.

Victoria Crater

In late September 2006, Opportunity wheeled up to Victoria Crater after 21 months on the road. It circled the rim for a few months snapping pictures and getting a close look at some layered rocks surrounding the crater. NASA then made a gutsy decision in June 2007 to take Opportunity inside the crater. It was a risk to the rover as it might not have been able to climb up again, but NASA said the science was worth it.

"The scientific allure is the chance to examine and investigate the compositions and textures of exposed materials in the crater's depths for clues about ancient, wet environments," NASA stated in a press release. "As the rover travels farther down the slope, it will be able to examine increasingly older rocks in the exposed walls of the crater."

The trek down was interrupted by a severe dust storm in July 2007. Opportunity's power-generating capabilities dropped by 80 percent in only one week as its solar panels became covered in dust. Late in the month, Opportunity's power dipped to critical levels. NASA worried the rover would stop working, but Opportunity pulled through.

It wasn't until late August that the skies cleared enough for Opportunity to resume work and head into the crater. Opportunity spent about a year wandering through Victoria Crater, getting an up-close look at the layers on the bottom and figuring that these were likely shaped by water.

Opportunity climbed out successfully in August 2008 and began a gradual journey to Endeavour, an incredible 13 miles (21 km) away. It took about three years to get there, as the rover was stopping to look at interesting science targets on the way. But Opportunity successfully arrived in August 2011.

NASA's Mars Exploration Rover Opportunity completed a drive on July 17 that took the vehicle's total driving distance on Mars past 20 miles.

Credit: NASA/JPL-Caltech

Exploring Endeavour, and memory resets

Opportunity's water history examinations continued at Endeavour, with one example being a 2013 probe of a rock called “Esperance.” The rock not only has clay minerals produced by water, but there was enough of the liquid to "flush out ions set loose by those reactions," stated Opportunity long-term planned Scott McLennan of the State University of New York, at the time.

By mid-year 2014, however, Opportunity was experiencing problems with its aging memory. The rover used Flash memory to store information when it went into hibernation during the Martian nights, which take place about as frequently as they do on Earth.

Controllers did a remote memory wipe from Earth, but memory issues and resets continued to plague the rover through the end of the year. Eventually, officials elected to stop using Flash memory, move storage over to random access memory (RAM) instead, and find a way to address the problem more thoroughly. In 2015, NASA decided to use RAM in most situations, which requires Opportunity to send high-priority data right away as the information cannot be stored if the rover is off.

Despite these issues, Opportunity continues rolling on the Red Planet. It set an off-world driving record in July 2014 when it successfully passed 25.01 miles (40.2 kilometers), exceeding the distance from the Soviet Union's remote-controlled lunar Lunokhod 2 rover in 1973. In March 2015, it passed another huge milestone: completing a marathon on Mars.

The rover successfully imaged Comet Siding Spring when the celestial body sped fairly close to Mars in October 2014. In January 2015, Opportunity took pictures from a "high point" on the rim of Endeavour, about 440 feet (134 feet) above the surrounding crater floor. In March 2015, NASA announced that the rover – while overlooking an area nicknamed "Marathon Valley" – had seen some rocks with a composition unlike others studied by Spirit or Opportunity; one of the features was high concentrations of aluminum and silicon.

After working through a Martian winter, in March 2016, Opportunity tackled its steepest slope ever — reaching a tilt of 32 degrees — while trying to reach a target on "Knudsen Ridge" inside Marathon Valley. As engineers watched the rover's wheels slip in the sand, they decided (with some reluctance) to skip the target and move to the next thing.

NASA announced it was wrapping up operations in Marathon Valley in June 2016, and added that Opportunity recently got a close-up look of "red-toned, crumbly material" on the southern slope of the valley. Opportunity scuffed some of this material with a wheel, revealing material with some of the highest sulfur content seen on Mars. NASA said the scuff had strong evidence of magnesium sulfate, a substance expected to precipitate from water.

As of August 2017, Opportunity was in a location called "Perseverance Valley" on the rim of Endeavour Crater, and the rover had traveled 27.95 miles (44.97 kilometers).

Additional resources

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The Amazing Mechanics of How and When Solar Eclipses Occur

The Amazing Mechanics of How and When Solar Eclipses Occur:

A solar eclipse makes a striking impression on the sky for those in its path — but how and when does it happen?

Credit: Robin Cordiner

As we are now less than a week away from "The Great American Eclipse" on Aug. 21, there will be countless articles appearing in newspapers, magazines and online talking about what causes a solar eclipse. I can remember as a young boy, not quite 7 years of age, having my grandfather explain the mechanics of what causes an eclipse using a salt shaker (for the moon), a pepper shaker (for Earth) and his fist for the sun.

By lining them up and placing the salt shaker between the pepper shaker and his fist, my grandfather explained that when such a lineup occurs in space, the moon will "get in the sun's way" and block out some or all of it, producing an eclipse of the sun.

Of course, there is a lot more to it than this. Just when, for example, do these alignments take place? [Total Solar Eclipse 2017: When, Where and How to See It (Safely)]

Eclipse seasons

If the moon orbited Earth in the same orbital plane in which Earth orbits the sun, an eclipse of the sun and an eclipse of the moon would each happen every month. But the moon's orbit is tilted slightly relative to that of Earth: by 5.15 degrees. As a result, at new moon phase, from our earthly vantage point, the moon usually appears to pass either above or below the sun in our sky and the moon's shadow misses Earth.

If the new moon crosses directly in front of the sun, then we have an eclipse (or as my grandfather would have said, "the moon will get in the sun's way"). In fact, when we see its silhouette in front of the sun, it's the only new moon that we can actually "see."

The accompanying table lists the eclipses for 2015, 2016 and 2017.

Three Years of Eclipses

Notice that the dates are not distributed randomly throughout the year, but are grouped at approximately half-year intervals. We cannot, for example, have an eclipse in September and another in December. For 2017, these "eclipse seasons" are in February and August.

Celestial crossing point

In our sky, there is an imaginary line that we call the ecliptic. That is the line that marks Earth's orbital path around the sun. The sun always remains on that ecliptic line, while the moon wanders above and below the ecliptic as a result of its orbital inclination. When the moon crosses the ecliptic — that is, when it reaches that point in its orbit where it passes through Earth's orbital plane — we call that point a "node." An eclipse can only occur when a new or full moon is near a node. On Aug. 21, the moon is new only about 8 hours after arriving at its ascending node, and the alignment of the moon and sun is good enough for a total eclipse. When we speak of an "ascending" node, that is the point where the moon crosses the ecliptic going from south to north. On Monday, that particular point will be in the constellation Leo, while the descending node is in Capricornus.

Now, go back and look at the table again. Note that the eclipse seasons occur a few weeks earlier each year. This is because the nodes are not stationary points at all. They move slowly westward, or "regress," along the ecliptic while the moon's inclination remains almost unchanged. This regression of the moon's nodes takes 18.6 years for one complete circuit; a complete nodal cycle. If, on the other hand, the orientation of the moon's orbit were fixed, then the eclipse seasons would come at the same time every year. [Science-Savvy Grandparents Explain Solar Eclipse in New Children's Book]

Earth versus sun: Moon caught in the middle

We can thank the gravitational tug-of-war between Earth and the sun for the changes wrought on the moon's orbital motion. Earth, of course, has greater influence on the moon because it is much closer to it than the sun. However, the sun still manages to perturb the lunar orbit in many other ways.

Along with the continual turning of the moon's orbital plane, even when the moon passes squarely across the face of the sun, the eclipse in question might not necessarily be total but annular; because the moon travels around the Earth in an elliptical orbit, it sometimes can be too far away from Earth for its dark umbral shadow to touch down on Earth's surface. The result? An annulus, or ring of sunlight that remains in view around the moon's silhouette. The major axis of the ellipse (the technical term is the line of the apsides) is also perturbed by the sun, and rotates eastward in the orbit plane in 8.85 years. Each month the dates of apogee (the moon's farthest point from Earth) and perigee (its closest point) occur a few days earlier relative to the dates of the moon's phases.

And just as the moon orbits Earth in an elliptical orbit, so does Earth similarly orbit the sun. We get as close as 91.4 million miles in early January and pull as far away as 94.5 million miles in early July. The difference amounts to less than 3.5 percent, but the sun's gravitational attraction varies inversely as the square of the distance, in this case about 7 percent. This annual oscillation in the sun's gravitation pull causes a perturbation in the moon's orbit known as the annual equation, and causes the moon to be slightly ahead of schedule from July to January and slightly behind at other times.

The sun not only alters the orientation of the moon's orbit, however, but also its shape; a perturbation called the evection. Also, because the moon is about a half million miles closer to the sun at new moon compared to full moon, the moon runs slightly ahead between new and first-quarter phases, and again between full and last quarter, an irregularity known as the variation. [Astronauts on the Space Station Will See the Solar Eclipse 3 Times]

Calculation complexities

You might think that these ever-so-slight differences in the motion of the moon have only been recently discovered, but, believe it or not, both the annual equation and the variation were known to the great Danish astronomer Tycho Brahe around the year 1600. The invention of the telescope was still a decade or so into the future, so Tycho used naked-eye instruments. Tycho was an assiduous observer of the sky, and was able to detect minute variations in the movements of the moon and the planets. And knowledge of the evection was known some 2,000 years ago to ancient Greek astronomers such as Ptolemy and Hipparchus.

Countless other minor perturbations come from factors such as the shape of Earth and the gravitational pulls from the other planets that can cause slight changes in the motion of the moon. Is it any wonder, then, that British mathematician and astronomer Ernest W. Brown, who devoted his life to studying the motion of the moon and putting together lunar tables, once commented that the time spent taking into account all of these planetary effects was liked "playing three-dimensional chess blindfolded."

So, as you watch the moon slowly cross in front of the sun on Monday, think back to this article and consider all the things that went into the calculation of this amazing celestial event.

Editor's note: Space.com has teamed up with Simulation Curriculum to offer this awesome Eclipse Safari app to help you enjoy your eclipse experience. The free app is available for Apple and Android, and you can view it on the web.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications, and he is also an on-camera meteorologist for Fios1 News in Rye Brook, New York. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

From Exoplanets to Galaxies: NASA Chooses 6 Missions for Further Study

From Exoplanets to Galaxies: NASA Chooses 6 Missions for Further Study:

NASA has selected six astrophysics proposals for concept studies under the agency's Explorers Program.

Credit: NASA

Six astrophysics programs selected for further study by NASA have science goals across the universe, ranging from exoplanets to galaxies.

This round of choices for NASA's Explorers Program, announced Aug. 9, includes three Explorer missions ($250 million each) and three missions of opportunity ($70 million each).

Each team has the chance to do a concept study. Scientific evaluations will be performed on each study, then NASA will select one Explorer mission and one mission of opportunity to fund in 2019. The expected launch dates would fall in 2022. [The Biggest Space Missions to Watch in 2017]

The three mission proposals (each receiving $2 million for the concept study), according to a NASA statement, are:

• Arcus. The mission would look at stars, galaxies and galaxy clusters with X-ray spectroscopy. The goal is to learn more about the gas around these objects, as well as how the gas and the objects interact. The principal investigator is Randall Smith, an astrophysicist at the Smithsonian Astrophysical Observatory in Massachusetts.
• Fast INfrared Exoplanet Spectroscopy Survey Explorer (FINESSE). This mission would study how planets are formed, their climate, and the origins and evolution of their atmospheres. Its goal is to get information about at least 500 exoplanets, ranging from super-Earths to gas giants. The principal investigator is Mark Swain, an exoplanet scientist at NASA's Jet Propulsion Laboratory (JPL) in California.
• Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx). This mission would image the sky in near-infrared wavelengths. This will reveal information about the beginnings of the universe, how galaxies formed and evolved, and would help reveal if other planets have life. The principal investigator is James Bock, an experimental cosmologist at the California Institute of Technology.

The three missions of opportunity (each receiving $500,000 for the concept study) are:

• Compton Spectrometer and Imager Explorer (COSI-X). This is a telescope that would be mounted in a balloon. The telescope would look at the sky in gamma-ray wavelengths. Its goal is to examine antimatter around the Milky Way's center and radioactive elements from supernovas (star explosions). The principal investigator is Steven Boggs, an astrophysicist at the University of California, Berkeley.
• Transient Astrophysics Observer on the International Space Station (ISS-TAO). This is an X-ray detector for the International Space Station whose primary goal is to look for X-rays that form when neutron stars merge with black holes or other neutron stars. It would also search for supernova shocks, neutron star bursts and gamma-ray bursts. The principal investigator is Jordan Camp, an astrophysicist at NASA's Goddard Space Flight Center in Maryland.
• Contribution to ARIEL Spectroscopy of Exoplanets (CASE). This would provide fine-guidance detectors for the proposed Atmospheric Remote Sensing Infrared Exoplanet Large-Survey (ARIEL) mission, which is led by the European Space Agency. ARIEL's main goal is to look at the wavelengths of light emitted by exoplanets, ranging from super-Earths to gas giants. CASE can proceed only if NASA selects it and if ESA decides to go ahead with ARIEL. The principal investigator is Swain.

Explorers is NASA's longest-running program. Its first mission was Explorer 1 in 1958, which also was the first U.S. satellite. Explorer 1 discovered the Van Allen radiation belts surrounding Earth. More than 90 missions have run under the program, including the Uhuru and Cosmic Background Explorer (COBE) missions that led to Nobel Prizes for their investigators.

"The Explorers Program brings out some of the most creative ideas for missions to help unravel the mysteries of the universe," Thomas Zurbuchen, associate administrator of NASA's science mission directorate, said in the statement. "The program has resulted in great missions that have returned transformational science, and these selections promise to continue that tradition."

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