Mars Express Captures Mars’ Moving Bow Shock

Mars Express Captures Mars’ Moving Bow Shock:

Every planet in our Solar System interacts with the stream of energetic particles coming from our Sun. Often referred to as “solar wind”, these particles consist mainly of electrons, protons and alpha particles that are constantly making their way towards interstellar space. Where this stream comes into contact with a planet’s magnetosphere or atmosphere, it forms a region around them known as a “bow shock”.

These regions form in front of the planet, slowing and diverting solar wind as it moves past – much like how water is diverted around a boat. In the case of Mars, it is the planet’s ionosphere that provides the conductive environment necessary for a bow shock to form. And according to a new study by a team of European scientists, Mars’ bow shock shifts as a result of changes in the planet’s atmosphere.

The study, titled “Annual Variations in the Martian Bow Shock Location as Observed by the Mars Express Mission“, appeared in the Journal of Geophysical Letters: Space Physics. Using data from the Mars Express orbiter, the science team sought to investigate how and why the bow shock’s location varies during the course of several Martian years, and what factors are chiefly be responsible.

Diagram of Mars’ orbit and changes to its bow shock between perihelion and aphelion. Credit: ESA/ATG medialab

For many decades, astronomers have been aware that bow shocks form upstream of a planet, where interaction between solar wind and the planet causes energetic particles to slow down and gradually be diverted. Where the solar wind meets the planet’s magnetosphere or atmosphere, a sharp boundary line is formed, which them extends around the planet in a widening arc.

This is where the term bow shock comes from, owing to its distinctive shape. In the case of Mars, which does not have a global magnetic field and a rather thin atmosphere to boot (less than 1% of Earth’s atmospheric pressure at sea level), it is the electrically-charged region of the upper atmosphere (the ionosphere) that is responsible for creating the bow shock around the planet.

At the same time, Mars relatively small size, mass and gravity allows for the formation of an extended atmosphere (i.e. an exosphere). In this portion of Mars’ atmosphere, gaseous atoms and molecules escape into space and interact directly with solar wind. Over the years, this extended atmosphere and Mars’ bow shock have been observed by multiple orbiter missions, which have detected variations in the latter’s boundary.

This is believed to be caused by multiple factors, not the least of which is distance. Because Mars has an relatively eccentric orbit (0.0934 compared to Earth’s 0.0167), its distance from the Sun varies quite a bit – going from 206.7 million km (128.437 million mi; 1.3814 AU) at perihelion to 249.2 million km (154.8457 million mi; 1.666 AU) at aphelion.

Illustration showing how Mars and Earth interact with solar wind. Credit: NASA

When the planet is closer, the dynamic pressure of the solar wind against its atmosphere increases. However, this change in distance also coincides with increases in the amount of incoming extreme ultraviolet (EUV) solar radiation. As a result, the rate at which ions and electrons (aka. plasma) are produced in the upper atmosphere increases, causing increased thermal pressure that counteracts the incoming solar wind.

Newly-created ions within the extended atmosphere are also picked up and accelerated by the electromagnetic fields being carried by the solar wind. This has the effect of slowing it down and causing Mars’ bowshock to shift its position. All of this has been known to happen over the course of a single Martian year – which is equivalent to 686.971 Earth days or 668.5991 Martian days (sols).

However, how it behaves over longer periods of time is a question that was previously unanswered. As such, the team of European scientists consulted data obtained by the Mars Express mission over a five year period. This data was taken by the Analyser of Space Plasma and EneRgetic Atoms (ASPERA-3) Electron Spectrometer (ELS), which the team used to examine a total of 11,861 bow shock crossings.

What they found was that, on average, the bow shock is closer to Mars when it is near aphelion (8102 km), and further away at perihelion (8984 km). This works out to a variation of about 11% during the Martian year, which is pretty consistent with its eccentricity. However, the team wanted to see which (if any) of the previously-studied mechanisms was chiefly responsible for this change.

The moving Martian bow shock. Credit: ESA/ATG medialab

Towards this end, the team considered variations in solar wind density, the strength of the interplanetary magnetic field, and solar irradiation as primary causes – are all of which decline as the planet gets farther away from the Sun. However, what they found was that the bow shock’s location appeared more sensitive to variations in the Sun’s output of extreme UV radiation rather than to variations in solar wind itself.

The variations in bow shock distance also appeared to be related to the amount of dust in the Martian atmosphere. This increases as Mars approaches perihelion, causing the atmosphere to absorb more solar radiation and heat up. Much like how increased levels of EUV leads to an increased amount of plasma in the ionosphere and exosphere, increased amounts of dust appear to act as a buffer against solar wind.

As Benjamin Hall, a researcher at Lancaster University in the UK and the lead author of the paper, said in an ESA press release:

“Dust storms have been previously shown to interact with the upper atmosphere and ionosphere of Mars, so there may be an indirect coupling between the dust storms and bow shock location… However, we do not draw any further conclusions on how the dust storms could directly impact the location of the Martian bow shock and leave such an investigation to a future study.”

http://sci.esa.int/science-e-media/video/e6/108_Mars_BowShock_3d_512p24.mp4

In the end, Hall and his team could not single out any one factor when addressing why Mars’ bow shock shifts over longer periods of time. “It seems likely that no single mechanism can explain our observations, but rather a combined effect of all of them,” he said. “At this point none of them can be excluded.”

Looking ahead, Hall and his colleagues hope that future missions will help shed additional light on the mechanisms behind Mars shifting bowshock. As Hall indicated, this will likely involve “”joint investigations by ESA’s Mars Express and Trace Gas Orbiter, and NASA’s MAVEN mission. Early data from MAVEN seems to confirm the trends that we discovered.”

While this is not the first analysis that sought to understand how Mars’ atmosphere interacts with solar wind, this particular analysis was based on data obtained over a much longer period of time than any previously study. In the end, the multiple missions that are currently studying Mars are revealing much about the atmospheric dynamics of this planet. A planet which, unlike Earth, has a very weak magnetic field.

What we learn in the process will go a long way towards ensuring that future exploration missions to Mars and other planets that have weak magnetic fields (like Venus and Mercury) are safe and effective. It might even assist us with the creation of permanent bases on these worlds someday!

Further Reading: ESA, Journal of Geophysical Research: Space Physics

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Witnessing the 2017 Total Solar Eclipse Across America Mesmerizes Millions: Photo/Video Gallery

Witnessing the 2017 Total Solar Eclipse Across America Mesmerizes Millions: Photo/Video Gallery:

Solar corona and prominences during the total solar eclipse across America on Monday, August 21, 2017, as seen from Santee, South Carolina and 4.8 miles from the centerline. Credit: Ken Kremer/kenkremer.com

SANTEE, SOUTH CAROLINA – Witnessing ‘Totality’ during Monday’s ‘Great American Solar Eclipse’ was a truly mesmerizing experience far beyond anything I imagined and something I will never forget -That’s a sentiment shared by millions upon millions of fellow gushing spectators.

I was stationed in Santee, South Carolina, near Lake Marion and close to the centerline of Totality, along with space journalist friend and colleague Jeff Seibert. And we could not have asked for clearer skies to enjoy this awesome natural event made possible by a uniquely rare confluence of miraculous celestial mechanics.

Check out our expanding gallery of personal photos and videos as well as many more gathered from friends and colleagues herein.

Totality was mesmerizing! Although I fully hoped to see a science spectacle (weather permitting) – I wasn’t really prepared for the majesty of the ‘coronal fire’ of Totality on display in the sky that started with what seemed like a startling electric flash – – The sun was alive far beyond anything I imagined beforehand. An out of body experience truly beyond my wildest dreams.

And we really lucked out with the weather – – as the odds of good weather are apparently better near Lake Marion, local residents told me. Just 15 miles south in Saint George, SC where I held a well attended eclipse outreach event at my hotel the night before, it was sadly socked in.

Solar corona bursts out during the total solar eclipse across America on Monday, August 21, 2017, as seen from Santee, South Carolina and 4.8 miles from the centerline. Credit: Ken Kremer/kenkremer.com

Despite a less than promising weather forecast, the threatening Carolina storm clouds obscuring our sun as we awoke and got our camera gear together Monday morning, fortunately scooted away.

Just in the nick of time the rainy gray breakfast clouds miraculously parted as eclipse time approached and almost completely disappeared by lunchtime – fully an hour prior to the eclipses beginning from our viewing location in Santee; near beautiful Lake Marion, South Carolina, which intersects the heavily traveled I-95 North/South Interstate highway corridor.

Like tens of millions of others, I’ve seen several partial solar eclipses, but this was my first total solar eclipse and it did not disappoint!

And there is just no comparison between seeing a partial and a total solar eclipse – sort of like a family before and after having a baby.

Solar corona and multiple prominences visible during the total solar eclipse across America on Monday, August 21, 2017, as seen from Santee, South Carolina and 4.8 miles from the centerline. Credit: Ken Kremer/kenkremer.com

A few hundred excited people from across the East Coast including some families with kids had coincidentally gathered at our Santee location by the Water Park.

At Santee, SC, we enjoyed unobstructed totality for all 2 minutes, 34 seconds – very close to the longest possible duration of 2 min 43 seconds experienced by folks congregated in Carbondale, Illinois.

Overall our eclipse experience began at 1:14:55 p.m. EDT and concluded at 4:08:01 EDT – nearly three hours.

Totality started at 2:43:42 p.m. EDT and concluded at 2:46:16 p.m. EDT.

View shows partial solar eclipse as the moon begins obscuring the sun on the way to totality during the 2017 total solar eclipse on August 21, as seen from Santee, South Carolina and close to the centerline. Credit: Ken Kremer/kenkremer.com

At lunchtime it was a boiling hot, skin stinging 95+ degrees F. But barely half an hour into the eclipse and with the sun perhaps only a third covered the area noticeably cooled and darkened and the sunburn was gone.

As the eclipse deepened, the sky really darkened to the point we almost needed a flashlight and it was downright comfortable temperature wise.

I’m over the Moon so to speak and still replaying the totality event in my mind from start to finish.

You can follow along by watching this thrilling solar eclipse video produced by Jeff Seibert, and listen to the cheering crowd to get a sense of our Carolina Totality adventure:



Video Caption: Total Solar eclipse from Santee, SC on August 21, 2017. We were 4.8 miles South of the Umbra center line, and had clear weather until just before last contact. Credit: Jeff Seibert

At Santee we were 87% into the umbra with a 70 mile wide (115 km) lunar shadow path width, at 136 feet elevation above sea level.

There is just nothing like ‘Totality’ in my experience as a research scientist and journalist – working with and seeing cool science and space hardware up close.

Totality is a natural wonder of the Universe and it was an electrifying event.

At the moment that totality commenced, day turned almost instantly to night as though someone threw a light switch.

I distinctly heard crackling sounds burst through the air, akin to a thunderbolt clap at that very moment – heralding our sudden jolt to totality.

Cheers broke out. Everyone and myself were so totally in awe of totality. And the sun’s brilliant while corona suddenly became visible, alive and in motion as the solar surface was completely blocked, hidden behind our moon. So I just stared at the stunning beauty, barely able to function as a photographer.

The planet Venus quickly and suddenly and incredibly popped out brilliantly from the darkness of the daytime sky. Some stars were also visible.

You absolutely must experience this incomparable wonder of nature with you own eyeballs.

Focus on the fleeting moment.

Because in a flash of just 2.5 minutes #Eclipse2017 was gone & done!

The all natural light switch had been turned back on by mother nature herself.

If only a replay or restart were possible – someone in the crowd yelled in glee. And we all thought the same way.

Totality, like rockets and science can be addictive in a very positive way.

Furthermore, we also saw the famed partial solar crescents reflecting through trees onto the ground during the partial eclipse phases.

A sliver of the sun reappears after totality concludes during the 2017 total solar eclipse on August 21, as seen from Santee, South Carolina and close to the centerline. Credit: Ken Kremer/kenkremer.com

We very luckily enjoyed virtually perfect weather and clear blue skies for the entirely of the eclipse – from first contact, through totality and the last limb of contact of Earth’s moon covering the sun.

Only a few scattered cloud patches dotted overhead at the start and rapidly exited.

And very happily we were not alone.

The Aug. 21 ‘Total Solar ‘Eclipse Across America’ was enjoyed by tens of millions more lucky spectators, including many friends lining the solar eclipses narrow path of Totality from coast to coast.

The 70-mile-wide (115 km) swath of the Moons shadow raced across America from Oregon to South Carolina in a thrilling event that became sort of a communal experience with all the explanatory news coverage foreshadowing what was to come.

Everyone in North America was able to witness at least a partial solar eclipse, weather permitting- and many did either on there own or at special solar eclipse events organized at towns and cities at museums, parks and open spaces across the country.

12 million people live directly in the path of 2017 solar eclipse totality as it passed through 14 states.

It was the first total solar eclipse visible from the United States since Feb. 26, 1979. And it was the first such coast to coast eclipse crossing the entire continental United States in 99 years since June 8, 1918 during World War 1.

The umbra (or dark inner shadow) of the Moon moved west to east at 3000 MPH in Oregon and 1500 MPH by the time it reached our location in South Carolina.

The 2017 solar eclipse began on the west coast with the lunar shadow entering the US near Lincoln City, Oregon at 9:05 PDT, with totality beginning at 10:15 PDT, according to a NASA description.

Totality ended along the US East Coast in the coastal city of Charleston, South Carolina at 2:48 p.m. EDT. The last remnants of lunar shadow departed at 4:09 p.m. EDT. Charleston is about an hour or so east of my viewing location in Santee and folks there enjoyed stunning views too.

For as long as I live the 2017 Solar Eclipse Totality will be burned into my mind!

Partial solar eclipse as seen from Port Canaveral, Florida where a maximum of about 86% of the sun was covered during the 2017 total solar eclipse on August 21, 2017. Credit: Julia Bergeron

Partial solar eclipse as seen from Port Canaveral, Florida where a maximum of about 86% of the sun was covered during the 2017 total solar eclipse on August 21, 2017. Credit: Julia Bergeron

The 2017 Total solar eclipse as seen from a cell phone through eclipse glasses and reached about 86% of totality in this view from Titusville, Florida on Aug. 21, 2017. Credit: Ashley Carrillo

The 2017 Total solar eclipse as seen from a cell phone through eclipse glasses and reached about 86% of totality in this view from Titusville, Florida on Aug. 21, 2017. Credit: Ashley Carrillo

Watch for Ken’s continuing onsite TDRS-M, CRS-12, ORS 5 and NASA and space mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.

Watch for Ken’s

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

The 2017 Total solar eclipse as seen through eclipse glasses reached about 86% of totality in this view from Melbourne, Florida on Aug. 21, 2017. Credit: Julian Leek

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Learn more about the 2017 Total Solar Eclipse, upcoming Minotaur IV ORS-5 military launch on Aug. 25, recent ULA Atlas TDRS-M NASA comsat on Aug. 18, 2017 , SpaceX Dragon CRS-12 resupply launch to ISS on Aug. 14, NASA missions and more at Ken’s upcoming outreach events at Kennedy Space Center Quality Inn, Titusville, FL:

Aug 24-26: “2017 Total Solar Eclipse Minotaur IV ORS-5, TDRS-M NASA comsat, SpaceX CRS-12 resupply launches to the ISS, Intelsat35e, BulgariaSat 1 and NRO Spysat, SLS, Orion, Commercial crew capsules from Boeing and SpaceX , Heroes and Legends at KSCVC, ULA Atlas/John Glenn Cygnus launch to ISS, SBIRS GEO 3 launch, GOES-R weather satellite launch, OSIRIS-Rex, Juno at Jupiter, InSight Mars lander, SpaceX and Orbital ATK cargo missions to the ISS, ULA Delta 4 Heavy spy satellite, Curiosity and Opportunity explore Mars, Pluto and more,” Kennedy Space Center Quality Inn, Titusville, FL, evenings

Solar crescents projected on the ground after sunlight funnels through trees during the partial eclipse phases on Aug. 21, 2017. Credit: Julian Leek

Solar crescents projected onto the top of a picnic cooler and pine needles on the ground after sunlight funnels through trees during the partial eclipse phases on August 21 in Santee, SC. Credit: Ken Kremer/kenkremer.com

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New Study of Antares Creates the Best Map Ever of a Distant Star

New Study of Antares Creates the Best Map Ever of a Distant Star:

When stars exhaust their supply of hydrogen fuel, they exit the main sequence phase of their evolution and enter into what is known as the Red Giant Branch (RGB) phase. This is characterized by the stars expanding significantly and becoming tens of thousands of times larger than our Sun. They also become dimmer and cooler, which lends them a reddish-orange appearance (hence the name).

Recently, a team of astronomers used the ESO’s Very Large Telescope Interferometer (VLTI) to map one such star, the red supergiant Antares. In so doing, they were able to create the most detailed map of a star other than our Sun. The images they took also revealed some unexpected things about this supergiant star, all of which could help astronomers to better understand the dynamics and evolution of red giant stars.

The study which details their work, titled “Vigorous Atmospheric Motions in the Red Supergiant Supernova Progenitor Antares“, recently appeared in the journal Nature. As indicated in the study, the team – which was led by Keiichi Ohnaka, an associate professor at the UCN Institute of Astronomy in Chile = relied on the VLTI at the ESO’s Paranal Observatory in Chile to map Antares’s surface and measure the motions of its surface material.

Artist’s impression of the red supergiant star Antares, located 550 ly away in the constellation of Scorpius. Credit: ESO/M. Kornmesser

The purpose of their study was to chart how stars that have entered their RGB phase begin to change. The VLTI is uniquely suited to this task, since it is capable of combining light from four different telescopes – the 8.2-metre Unit Telescopes, or the smaller Auxiliary Telescopes – to create one virtual telescope that has the resolution of a telescope lens measuring 200 meters across.

This allows the VLTI to resolve fine details far beyond what can be seen with a single telescope. As Prof. Ohnaka explained in a recent ESO press statement:

“How stars like Antares lose mass so quickly in the final phase of their evolution has been a problem for over half a century. The VLTI is the only facility that can directly measure the gas motions in the extended atmosphere of Antares — a crucial step towards clarifying this problem. The next challenge is to identify what’s driving the turbulent motions.”

For their study, the team relied on three of the VLTI Auxiliary Telescopes and an instrument called the Astronomical Multi-BEam combineR (AMBER). This near-infrared spectro-interferometric instrument combines three telescopic beams coherently, allowing astronomers to measure the visibilities and closure phases of stars. Using these instruments, the team obtained images of Antares’ surface over a small range of infrared wavelengths.

From these, the team was able to calculate the difference between the speed of atmospheric gas at different locations on Antares’ surface, as well as its average speed over the entire surface. This resulted in a two-dimensional velocity map of Antares, which is the first such map created of another star other than the Sun. As noted, it is also the most-detailed map of any star beyond our Solar System to date.

The study also made some interesting discoveries of what takes place on Antares’ surface and in its atmosphere. For example, they found evidence for high-speed upwellings of gas that reached distances of up to 1.7 Solar radii into space – much farther than previously thought. This, they claimed, could not be explained by convection alone, the process whereby cold material moves downwards and hot material upwards in a circular pattern.

This process occurs on Earth in the atmosphere and with ocean currents, but it is also responsible for moving pockets of hotter and colder gas around within stars. The fact that convection cannot explain the behavior of Antares extended atmosphere would therefore suggests that some new and unidentified process common to red giant stars must be responsible.

These results therefor offer new opportunities for research into stellar evolution, which is made possible thanks to next-generation instruments like the VTLI. As Ohnaka concluded:

“In the future, this observing technique can be applied to different types of stars to study their surfaces and atmospheres in unprecedented detail. This has been limited to just the Sun up to now. Our work brings stellar astrophysics to a new dimension and opens an entirely new window to observe stars.”

Not only is this kind of research improving our understanding of stars beyond our Solar System, it lets us know what to expect when our Sun exits it main sequence phase and begins expanding to become a red giant. Though that day is billions of years away and we can’t be certain humanity will even be around by that time, knowing the mechanics of stellar evolution is important to our understanding of the Universe.

It pays to know that even after we are gone, we can predict what will still be here and for how long. Be sure to check out this 3D animation of Antares, courtesy of the ESO:

Further Reading: ESO, Nature

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Dragonfly Proposed to NASA as Daring New Frontiers Mission to Titan

Dragonfly Proposed to NASA as Daring New Frontiers Mission to Titan:

In late 1970s and early 80s, scientists got their first detailed look at Saturn’s largest moon Titan. Thanks to the Pioneer 11 probe, which was then followed by the Voyager 1 and 2 missions, the people of Earth were treated to images and readings of this mysterious moon. What these revealed was a cold satellite that nevertheless had a dense, nitrogen-rich atmosphere.

Thanks to the Cassini-Huygens mission, which reached Titan in July of 2004 and will be ending its mission on September 15th, the mysteries of this moon have only deepened. Hence why NASA hopes to send more missions there in the near future, like the Dragonfly concept. This craft is the work of the John Hopkins University Applied Physics Laboratory (JHUAPL), which they just submitted an official proposal for.

Essentially, Dragonfly would be a New Frontiers-class mission that would use a dual-quadcopter setup to get around. This would enable vertical-takeoff and landing (VTOL), ensuring that the vehicle would be capable of exploring Titan’s atmosphere and conducting science on the surface. And of course, it would also investigate Titan’s methane lakes to see what kind of chemistry is taking place within them.

Image of Titan’s atmosphere, snapped by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute

The goal of all this would be to shed light on Titan’s mysterious environment, which not only has a methane cycle similar to Earth’s own water cycle, but is rich in prebiotic and organic chemistry. In short, Titan is an “ocean world” of our Solar System – along with Jupiter’s moons Europa and Ganymede, and Saturn’s moon of Enceladus – that could contain all the ingredients necessary for life.

What’s more, previous studies have shown that the moon is covered in rich deposits of organic material that are undergoing chemical processes, ones that might be similar to those that took place on Earth billions of years ago. Because of this, scientists have come to view Titan as a sort of planetary laboratory, where the chemical reactions that may have led to life on Earth could be studied.

As Elizabeth Turtle, a planetary scientist at JHUAPL and the principal investigator for the Dragonfly mission, told Universe Today via email:

“Titan offers abundant complex organics on the surface of a water-ice-dominated ocean world, making it an ideal destination to study prebiotic chemistry and to document the habitability of an extraterrestrial environment. Because Titan’s atmosphere obscures the surface at many wavelengths, we have limited information about the materials that make up the surface and how they’re processed.  By making detailed surface composition measurements in multiple locations, Dragonfly would reveal what the surface is made of and how far prebiotic chemistry has progressed in environments that provide known key ingredients for life, identifying the chemical building blocks available and processes at work to produce biologically relevant compounds.”

In addition, Dragonfly would also use remote-sensing observations to characterize the geology of landing sites. In addition to providing context for the samples, it would also allow for seismic studies to determine the structure of the Titan and the presence of subsurface activity. Last, but not least, Dragonfly would use meteorology sensors and remote-sensing instruments to gather information on the planet’s atmospheric and surface conditions.

The Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR) is another concept for an aerial explorer for Titan. Credit: Mike Malaska

While multiple proposals have been made for a robotic explorer mission of Titan, most of these have taken the form of either an aerial platforms or a combination balloon and a lander. The Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR), a proposal made in the past by Jason Barnes and a team of researchers from the University of Idaho, is an example of the former.

In the latter category, you have concepts like the Titan Saturn System Mission (TSSM), a concept that was being jointly-developed by the European Space Agency (ESA) and NASA. An Outer Planets Flagship Mission concept, the design of the TSSM consisted of three elements – a NASA orbiter, an ESA-designed lander to explore Titan’s lakes, and an ESA-designed Montgolfiere balloon to explore its atmosphere.

What separates Dragonfly from these and other concepts is its ability to conduct aerial and ground-based studies with a single platform. As Dr. Turtle explained:

“Dragonfly would be an in situ mission to perform detailed measurements of Titan’s surface composition and conditions to understand the habitability of this unique organic-rich ocean world.  We proposed a rotorcraft to take advantage of Titan’s dense, calm atmosphere and low gravity (which make flight easier on Titan than it is on Earth) to convey a capable suite of instruments from place to place — 10s to 100s of kilometers apart — to make measurements in different geologic settings.  Unlike other aerial concepts that have been considered for Titan exploration (of which there have been several), Dragonfly would spend most of its time on the surface performing measurements, before flying to another site.”

Dragonfly‘s suite of instruments would include mass spectrometers to study the composition of the surface and atmosphere; gamma-ray spectrometers, which would measure the composition of the subsurface (i.e. looking for evidence of an interior ocean); meteorology and geophysics sensors, which would measure wind, atmospheric pressure, temperature and seismic activity; and a camera suite to snap pictures of the surface.

Artist’s concept of the Titan Aerial Daughter quadcopter and its “Mothership” balloon. Credit: NASA/STMD

Given Titan’s dense atmosphere, solar cells would not be an effective option for a robotic mission. As such, the Dragonfly would rely on a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) for power, similar to what the Curiosity rover uses. While robotic missions that rely on nuclear power sources are not exactly cheap, they do enable missions that can last for years at a time and conduct invaluable research (as Curiosity has shown).

As Peter Bedini – the Program Manager at the JHUAPL Space Department and Dragonfly’s project manager – explained, this would allow for a long-term mission with significant returns:

“We could take a lander, put it on Titan, take these four measurements at one place, and significantly increase our understanding of Titan and similar moons. However, we can multiply the value of the mission if we add aerial mobility, which would enable us to access a variety of geologic settings, maximizing the science return and lowering mission risk by going over or around obstacles.”

In the end, a mission like Dragonfly would be able to investigate how far prebiotic chemistry has progressed on Titan. These types of experiments, where organic building blocks are combined and exposed to energy to see if life emerges, cannot be performed in a laboratory (mainly because of the timescales involved). As such, scientists hope to see how far things have progressed on Titan’s surface, where prebiotic conditions have existed for eons.

Titan’s thick, nitrogen and hydrocarbon-rich atmosphere lends the planet a cloudy, yellowsh-brown appearance. Credit: NASA/JPL-Caltech/Space Science Institute

In addition, scientists will also be looking for chemical signatures that indicate the presence of water and/or hydrocarbon-based life. In the past, it has been speculated that life could exist within Titan’s interior, and that exotic methanogenic lifeforms could even exist on its surface. Finding evidence of such life would challenge our notions of where life can emerge, and greatly enhance the search for life within the Solar System and beyond.

As Dr. Turtle indicated, mission selection will be coming soon, and whether or not the Dragonfly mission will be sent to Titan should be decided in just a few years time:

“Later this fall, NASA will select a few of the proposed New Frontiers missions for further work in Phase A Concept Studies” she said. “Those studies would run for most of 2018, followed by another round of review.  And the final selection of a flight mission would be in mid-2019… Missions proposed to this round of the New Frontiers Program would be scheduled to launch before the end of 2025.”

And be sure to check out this video of a possible Dragonfly mission, courtesy of the JHUAPL:



Further Reading: JHU Hub

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Is the “Alien Megastructure” around Tabby’s Star Actually a Ringed Gas Giant?

Is the “Alien Megastructure” around Tabby’s Star Actually a Ringed Gas Giant?:

KIC 8462852 (aka. Tabby’s Star) continues to be a source of both fascination and controversy. Ever since it was first seen to be undergoing strange and sudden dips in brightness (in October of 2015) astronomers have been speculating as to what could be causing this. Since that time, various explanations have been offered, including large asteroids, a large planet, a debris disc or even an alien megastructure.

The latest suggestion for a natural explanation comes from the University of Antioquia in Colombia, where a team of researchers have proposed that both the larger and smaller drops in brightness could be the result of a ringed planet similar to Saturn transiting in front of the star. This, they claim, would explain both the sudden drops in brightness and the more subtle dips seen over time.

The study, titled “Anomalous Lightcurves of Young Tilted Exorings“, recently appeared online. Led by Mario Sucerquia, a postdoctoral student at the University of Antioquia’s Department of Astronomy, the team performed numerical simulations and semi-analytical calculations to determine if a the transits of a ringed gas giant could explain the recent observations made of Tabby’s Star.

An artist impression of an exomoon orbiting a ringed exoplanet. Credit: Andy McLatchie

Currently, exoplanet-hunters use a number of methods to detect planetary candidates. One of the most popular is known as the Transit Method, where astronomers measure dips in a star’s brightness caused by a planet passing between it and the observer (i.e. transiting in front of a star). How a gas giant with rings would dim a star’s light was of concern here because it would do so in an irregular way.

Basically, the rings would be the first thing to obscure light coming from the star, but only to a small degree. Once the bulk of the gas giant transited the star, a significant drop would occur followed a second smaller drop as the rings on the other side passed by. But since the rings would be at a different angle every time, the smaller dips would be larger or smaller and the only way to know for sure would be to compare multiple transits.

In the past, researchers from the University of Antioquia developed a novel method for detecting rings around exoplanets (“exorings”). Essentially, they showed how an increase in the depth of a transit signal and the so-called “photo-ring” effect (often mistaken for false-positives in previous surveys) could be interpreted as signs of an exoplanet with a Saturn-like ring structure.

The team that devised this method was led by Jorge I. Zuluaga of the Harvard Smithsonian Center for Astrophysics (CfA), who was also a co-author on this study.  To test this theory with KIC 8462852, the team simulated a light curve from a ringed planet that was about 0.1 AU from the star. What they found was that a tilted ring structure could explain the dimming effects detected from Tabby’s Star in the past.

Artist’s impression of an exoplanet with an extensive ring system. Credit and Copyright: Ron Miller

They also found that a tilted ring structure would undergo short-term changes in shape and orientation as a result of the star’s gravitational tug on them. These would be apparent due to strong variations of transit depth and contact times even between consecutive transits. This too would likely be interpreted as anomalies in signal data, or lead to miscalculations of a planet’s properties (i.e. radius, semi-major axis, stellar density, etc).

This is not the first time that a ringed-structure has been suggested as an explanation for the mystery that is Tabby’s Star. And the team admits that there are other possible explanations, which include the possibility of an exomoon breaking up around a larger planet (i.e. leaving a debris disk). But as Sucerquia indicated in an interview with New Scientist, this latest study does offer some compelling food for thought:

“The point of this work is to show the community that there are mechanisms that can alter the light curves. These changes can be generated by the dynamics of the moons or the rings, and the changes in these systems can occur in such short scales as to be detected in just a few years.”

Another interesting takeaway from the research study is the fact that oscillating ring structures could also account for the strangeness of some light-curves that are already known. In other words, its possible that astronomers have already found evidence of ringed exoplanets, and simply didn’t know it. Looking ahead, it is possible that future surveys could turn up plenty more of these worlds as well.

Of course, if this study should prove to be correct, it means that what some consider our best hope of finding an alien megastructure has now been lost. Admittedly, this would be a disappointment. If there’s one thing about the mystery of Tabby’s Star that has been consistently intriguing, it’s the fact that a megastructure couldn’t be ruled out. If we have come to that point at last, there’s not much more to say.

Except, perhaps, that’s it’s a big Universe! There’s sure to be a Kardashev Type II civilization out there somewhere!

Further Reading: New Scientists, arXiv

The post Is the “Alien Megastructure” around Tabby’s Star Actually a Ringed Gas Giant? appeared first on Universe Today.

Here's a Weather Update for Solar Eclipse Day (Aug. 21, 2017)

Here's a Weather Update for Solar Eclipse Day (Aug. 21, 2017):

A cloudy partial solar eclipse.

Credit: Deacon MacMillan/Flickr

With eclipse day fast approaching, many people are obviously concerned about how the weather will impact their viewing. Here's how it's looking for locations all along the eclipse path. Before getting into this, however, I want to make sure anyone reading this acknowledges a "reality check" that this event is still three days away, and forecasters are not overly confident on some of the finer details. Over the weekend, this confidence will increase, especially as Monday comes into the time range of various shorter-term, higher-resolution computer models.

Pacific Northwest/Rocky Mountains/Northern Great Plains

The Oregon/Idaho/Wyoming part of the total eclipse path will experience a high-pressure ridge over the Pacific Northwest on Monday, according to the National Weather Service. There will also be a weak low off the Southern California coast that sends some monsoon moisture north from the desert Southwest — but all models keep the moisture south of the Oregon/Nevada border. That should ensure mostly clear skies for much of Oregon come Monday morning. The exception to this would be marine clouds coming onshore along Oregon's central coast. From a climatological point of view, however, marine clouds don't make it very far inland, so locations from the Coast Range eastward appear to have a very good chance of clear skies for the eclipse Monday morning.

For Idaho, haze and smoke could be present from area wildfires. It looks like the best cloud/storm chances will remain across the southern highlands and perhaps out of the totality path. [Solar Eclipse 2017: Traffic and Weather Forecasts for States in Totality]

As for Wyoming, the main weather concern for eclipse day will be a threat for scattered to occasionally broken cloud cover. For now, the consensus is a 30 to 60 percent cloud cover along the path of totality during the eclipse. Most of these clouds will be of the high and mid cloud variety with cumulus cloud buildups, mainly over the mountains, where only isolated shower or thunderstorm activity is expected.

Central Great Plains

Pushing into Nebraska/Kansas/Missouri and southern Illinois, the situation becomes more problematic, as a storm system is expected to move across northern Nebraska Monday morning. So those living near and along the totality path in Nebraska may have to deal with some potential storms and cloudiness early on Monday. The big question that we're focusing on right now is whether the clouds can clear enough later Monday morning after the rain in time for the eclipse.

Based on the latest guidance models, it seems that yes, there may be morning clouds and storms, but there's a decent chance that they will begin to scatter or break up by late morning. Obviously, trying to predict a cloud forecast with certainty for a 2-minute window that's still a few days away is a significant challenge.

Looking at Kansas and Missouri, this same unsettled weather system will be a factor. That, combined with a strong southerly wind, brings increasing low-level moisture for Sunday night into Monday. The GFS (Global Forecast System) and Canadian models are more bullish on rain and cloud-cover chances; this may be an issue for eclipse watchers.

But the Nebraska storm is expected to shift rapidly into Iowa by late Monday. As such, there is better support for good eclipse viewing for areas farther east into east-central and southeast Missouri, as well as southern Illinois, which should be farther away from what could be isolated thunderstorms. Western and central Missouri look to be in the worst spot in this four-state region. [Total Solar Eclipse 2017: When, Where and How to See It (Safely)]

Ohio and Tennessee valleys

Looking farther east at Kentucky and Tennessee, high pressure at the surface and aloft is expected to remain in place across the region. Kentucky looks to remain on the northern periphery of the ridge, and some of the model data suggest that isolated afternoon or evening storms could occur. Skies look to remain mainly clear in the morning, with cumulus clouds popping up during the afternoon.

In general terms, it looks like very typical weather for late August in the Ohio Valley. However, the development of these clouds is dependent on warming from the afternoon sun, and of course, solar heating will be reduced during Monday afternoon. Cumulus clouds may begin to form and then dissipate as the air cools in response to the eclipse. The same holds true for Tennessee, with 30 to 40 percent cloud cover currently anticipated, with only a slight probability (20 percent or less) for most of this region.

Piedmont and Southeast coast 

Our final stop is northeast Georgia and the Carolinas. Unfortunately, a stalled weather front is running from northern sections of Georgia and South Carolina east through the south end of North Carolina. And that front quite possibly could generate scattered afternoon showers and thunderstorms, which may wreak havoc for those wanting to witness the eclipse.

In this type of summer/sultry pattern, it is always difficult to discern, especially a few days out, specifically the different cloud and precipitation coverage. On a positive note, there are signs that an offshore ridge of high pressure will try to build in, possibly suppressing somewhat any cloud or shower development. The eclipse could also aid in keeping the threat of daytime clouds and shower development down by helping to lower temperatures in similar fashion to what we noted for Kentucky and Tennessee. Still, based on the projected setup, it is prudent to mention at least a 30 to 35 percent chance of showers and thunderstorms. Based on long-term climatological records, the best chance of encountering building afternoon clouds and showers will be over the high-terrain areas (Blue Ridge, Appalachian and Great Smoky mountains), while the best chance of getting some views of the sun will be along the coastal plain.

Some useful websites

Here are some websites related to weather and the upcoming Great American Solar Eclipse that may interest you:

National Weather Service Eclipse Page

Joe Rao's Eclipse Tutorial and Weather Prospects in Weatherwise Magazine

Jay Anderson's Great American Eclipse Weather Page

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

Cassini-Huygens: Exploring Saturn's System

Cassini-Huygens: Exploring Saturn's System:

Artist's concept of NASA's Cassini spacecraft at Saturn.

Credit: NASA/JPL

The Cassini spacecraft has been orbiting Saturn since 2004. The mission is known for discoveries such as finding jets of water erupting from Enceladus, and tracking down a few new moons for Saturn. Now low on fuel, the spacecraft will make a suicidal plunge into the ringed planet in 2017 and capture some data about Saturn's interior on the way. (This will avoid the possibility of Cassini crashing someday onto a potentially habitable icy moon, such as Enceladus or Rhea.)

The ambitious mission is a joint project among several space agencies, which is a contrast from the large NASA probes of the past such as Pioneer and Voyager. In this case, the main participants are NASA, the European Space Agency and Agenzia Spaziale Italiana (the Italian space agency).

Development history

Cassini is the first dedicated spacecraft to look at Saturn and its system. It was named for Giovanni Cassini, a 17th-century astronomer who was the first to observe four of Saturn's moons — Iapetus (1671), Rhea (1672), Tethys (1684) and Dione (1684).

Before this spacecraft came several flybys of Saturn by Pioneer 11 (1979), Voyager 1 (1980) and Voyager 2 (1981). Some of the discoveries that came out of these missions included finding out that Titan's surface can't be seen in visible wavelengths (due to its thick atmosphere), and spotting several rings of Saturn that were not visible with ground-based telescopes.

It was shortly after the last flyby, in 1982, that scientific committees in both the United States and Europe formed a working group to discuss possible future collaborations. The group suggested a flagship mission that would orbit Saturn, and would send an atmospheric probe into Titan. However, there was a difficult "fiscal climate" in the early 1980s, NASA's Jet Propulsion Laboratory noted in a brief history of the mission, which pushed approval of Cassini to 1989.

The Europeans and the Americans each considered either working together, or working solo. A 1987 report by former astronaut Sally Ride, for example, advocated for a solo mission to Saturn. Called "NASA's Leadership and America's Future in Space," the report said that studying the outer gas giant planets (such as Saturn) help scientists learn about their atmospheres and internal structure. (Today, we also know that this kind of study helps us predict the structure of exoplanets, but the first exoplanets were not discovered until the early 1990s.)

"Titan is an especially interesting target for exploration because the organic chemistry now taking place there provides the only planetary-scale laboratory for studying processes that may have been important in the prebiotic terrestrial atmosphere," the report added, meaning that on Titan is chemistry that could have been similar to what was present on Earth before life arose.

Cassini's development came with at least two major challenges to proceeding. By 1993 and 1994, the mission had a $3.3 billion price tag (roughly $5 billion in 2017 dollars, or about half the cost of the James Webb Space Telescope.) Some critics perceived this as overly high for the mission. In response, NASA pointed out that the European Space Agency was also contributing funds, and added that the technologies from Cassini were helping to fund lower-cost NASA missions such as the Mars Global Surveyor, Mars Pathfinder and the Spitzer Space Telescope, according to JPL.

Cassini also received flak from environmental groups who were concerned that when the spacecraft flew by Earth, its radioisotope thermoelectric generator (nuclear power) could pose a threat to our planet, JPL added. These groups filed a legal challenge in Hawaii shortly before launch in 1997, but the challenge was rejected by the federal district court in Hawaii and the Ninth Circuit Court of Appeals.

To address concerns about the spacecraft's radioisotope thermoelectric generators, which are commonly used for NASA missions, NASA responded by issuing a supplementary document about the flyby and detailing the agency's methodology for protecting the planet, saying there was less than a one-in-a-million chance of an impact occurring.

Saturn's largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA's Cassini spacecraft. This view looks toward the northern, sunlit side of the rings from just above the ring plane. It was taken on May 21, 2011, when Cassini was about 1.4 million miles (2.3 million kilometers) from Titan.

Credit: NASA/JPL-Caltech/Space Science Institute

Launch and cruise

Cassini didn't head straight to Saturn. Rather, its mission involved complicated orbital mechanics. It went past several planets — including Venus (twice), Earth and Jupiter — to get a speed boost by taking advantage of each planet's gravity.

The nearly 12,600-lb. (about 5,700 kilograms) spacecraft was hefted off Earth on Oct. 15, 1997. It went by Venus in April 1998 and June 1999, Earth in August 1999 and Jupiter in December 2000.

Cassini settled into orbit around Saturn on July 1, 2004. Among its prime objectives were to look for more moons, to figure out what caused Saturn's rings and the colors in the rings, and understanding more about the planet's moons.

Perhaps Cassini's most detailed look came after releasing the Huygens lander toward Titan, Saturn's largest moon. The lander was named for Dutch scientist Christiaan Huygens, who in 1654 turned a telescope toward Saturn and observed that its odd blob-like shape — Galileo Galilei had first seen the shape in a telescope and drew it in his notebook as something like ears on the planet — was in fact caused by rings.

The Huygens lander descended through the mysterious haze surrounding the moon and landed on Jan. 14, 2005. It beamed information back to Earth for nearly 2.5 hours during its descent, and then continued to relay what it was seeing from the surface for 1 hour 12 minutes.

In that brief window of time, researchers saw pictures of a rock field and got information back about the moon's wind and gases on the atmosphere and the surface.

This first panorama of Titan released by ESA shows a full 360-degree view around the Huygens probe. The left-hand side shows a boundary between light and dark areas. The white streaks seen near this boundary could be ground 'fog', as they were not immediately visible from higher altitudes. Huygens drifted over a plateau (centre of image) and was heading towards its landing site in a dark area (right) during descent.

Credit: ESA/NASA/University of Arizona.

Magnificent moons

One of the defining features of Saturn is its number of moons. Excluding the trillions of tons of little rocks that make up its rings, Saturn has 62 discovered moons as of September 2012. NASA lists 53 named moons on one of its websites.

In fact, Cassini discovered two new moons almost immediately after arriving (Methone and Pallene) and before 2004 had ended, it detected Polydeuces. [Gallery: Latest Saturn Photos from NASA's Cassini Orbiter]

As the probe wandered past Saturn's moons, the findings it brought back to Earth revealed new things about their environments and appearances. Some of the more notable findings include:

Saturn has not gone ignored, either. For example, in 2012, a NASA study postulated that Saturn's jet streams in the atmosphere may be powered by internal heat, instead of energy from the sun. Scientists believe that heat brings up water vapor from the inside of the planet, which condenses as it rises and produces heat. That heat is believed to be behind jet stream formation, as well as that of storms.

Mission extension and end

Cassini was originally slated to last four years at Saturn, until 2008, but its mission has been extended multiple times. Its last and final leg was called the Cassini Solstice Mission, named because the planet and its moons reached the solstice again toward the mission end. Saturn orbits the sun every 29 Earth-years. With Cassini's mission lasting 13 years, this meant that the spacecraft observed almost half of Saturn's seasonal change as the planet went around its orbit.

In 2016, the spacecraft was set on a series of final maneuvers to provide close-up views of the rings, with the ultimate goal of plunging Cassini into Saturn on Sept. 15, 2017. This protected Enceladus and other potentially habitable moons from the (small) chance of Cassini colliding with the surface, spreading Earth microbe.

Major milestones of the finale included:

• Ring-grazing orbits: Every week between Nov. 30, 2016, and April 22, 2017, Cassini did loops around Saturn's poles to look at the outer edge of the rings, to learn more about their particles, gases and structure. It also observed small moons in this region, including Atlas, Daphnis, Pan and Pandora.
• On April 22, 2017, Cassini made the final flyby of Titan. The flyby was done in such a way to change Cassini's orbit so that it began 22 dives (once a week) between the planet and its rings. This was the first time any spacecraft explored this zone, and it entailed some risk because the orbit brought it between the outer part of the atmosphere and the inner zone of the rings (where it is at risk of striking particles or gas molecules). 
• On Sept. 15, 2017, Cassini will make a suicidal plunge into Saturn, taking measurements for as long as its instruments can make communications back to Earth.

Some of the science Cassini performed during this period included creating maps of the planet's gravity and magnetic fields, estimating how much material is in the rings, and taking high-resolution images of Saturn and its rings from close-up.

The spacecraft made an interesting discovery from its new vantage point. It found that Saturn's magnetic field is closely aligned with the planet's axis of rotation, which baffled scientists because of how they think magnetic fields are generated — through a difference of tilt between the magnetic field and a planet's rotation. As of late July 2017, however, scientists planned to gather more data to see if perhaps Saturn's internal processes confused their measurements.

Additional resource

How Astronomers Use Eclipses to Discover Alien Worlds

How Astronomers Use Eclipses to Discover Alien Worlds:

Artist's illustration of the star system Kepler-444, whose five planets were discovered by the Kepler space telescope as they passed in front of their star, dimming its light. All five orbit the star within less than 10 days.

Credit: Tiago Campante/Peter Devine

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.

As we prepare for the upcoming total solar eclipse set to cross the continental United States on Aug. 21, the mechanics of the event are pretty straightforward to explain: Occasionally the sun, moon and Earth end up in straight line, and when they do, the moon casts its shadow on the Earth. Voila: eclipse!

From our perspective here on the surface of the Earth, it appears as if the disk of the moon covers the face of the sun. You have to be near or at totality — when the sun is fully covered — to notice the sun's dimming with your unaided eyes. However, sophisticated light-measuring instruments can easily pick up even the slightest hint of reduction in sunlight no matter the extent of the eclipse.

Now let's play a game. Let's say you attached these keen instruments to a telescope and you rocketed a few light-years away from the solar system. And instead of observing the sun-moon eclipse, you stared at the sun as the Earth meandered in its orbit. If you lined everything up just right and stared long enough, eventually you would get to see the tiny planet cross the face of its massive sun. [Total Solar Eclipse 2017: Here Are the Best Live-Video Streams to Watch]

With enough dedication to your astronomical duties, you could conceivably measure a dip in brightness as the Earth entered the edge of the sun, and a return to normalcy as the planet moved on.

Let's take it to the extreme: You're so far away that you can't even see a tiny dot representing the Earth. Could you still measure the telltale dip in brightness? Well, measuring the light output of a star is much easier than hunting for an insignificant speck of a rocky world, so I suppose with enough technological progress one could achieve it.

And imagine this: What if we did this all the time? Well, we do. This hunting for subtle eclipses is our primary method for detecting exoplanets — planets outside the solar system, orbiting their own host stars. Of course, astronomers don't call it "subtle eclipse method," but rather the "transit method."

This method allows us to find exoplanets big and small orbiting stars of all sizes and ages. Over 4,000 planets and counting! We haven't found an exact match for Earth yet — but we're getting closer to finding a match with every new planet detected.

The transit method isn't perfect, of course; it relies on a chance alignment among the star, the exoplanet and us. If that planet just happens to orbit perpendicular to our line of sight, we're out of luck. Thankfully, there are, to put it mildly, many stars out there, even within our nearby galactic neighborhood, so enough coincidences occur to give us a solid census of our celestial cousins.

So, as you're feasting your eyes on the upcoming solar eclipse, you might wonder if some distant observer is also enjoying the event.

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

Here's What It's Like to Be the Planetary Protection Officer at NASA

Here's What It's Like to Be the Planetary Protection Officer at NASA:

Credit: Reid Wiseman/NASA

If you want a job protecting Earth from threats from outer space — or even protecting Mars from us — NASA has an opening for you — sort of. The job of planetary protection officer generated quite a bit of buzz last week, when the public learned that a role seemingly out of a science fiction novel was actually a bonafide NASA job. But the position has nothing to do with protecting Earth from little green men, but a whole lot to do with important interplanetary science.

A primary task of the officer is to make sure that during NASA missions earthly microbes don't contaminate potentially habitable environments. And should a mission bring back samples from outer space, the officer is tasked with making sure that dust, or rocks, or whatever is brought back from outer space doesn't contaminate us.

John Rummel, a biology professor at East Carolina University, held the position twice, first between 1990 and 1993 and again from 1998 to 2006.

"The planetary protection job was mostly challenging in that it was not just important for each mission to do the right — required by requirements — thing, but to know why they were doing it, and why it was important to do a good job," Rummel said. "From that aspect, the job was definitely worth it. But as to 'rewards,' those were mostly internal.”

Rummel explained that the planetary protection office reports to the associate administrator for each mission, who oversees the cost of the project. That means recommendations made by the officer are often judged in the context of whether or not they will cost the administrator more money — a vexing problem many of us might easily understand from our own work experiences.

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

Rummel's time as planetary protection officer coincided with the restart of NASA's Mars program.

After the successful twin Viking landings of the 1970s, a few famous searching-for-life experiments came up empty. NASA shifted its attention to other locations in the solar system, and Mars didn't get a launch opportunity until the failed Mars Observer mission in 1992.

A slew of missions followed, however, including the Mars Pathfinder mission that made it all the way to the surface in 1996 and deployed a mini-rover – Sojourner. Several other landing and orbiting missions followed — some successful, others not.

Those missions wouldn't have been possible without the approval of the planetary protection officer, who ensured that Sojourner and other Martian spacecraft were sterile enough to prevent microbes from taking root in potentially life-friendly areas. One of Rummel's first tasks in 1990 was to look at the risk of contamination on Mars and how scientific understanding had changed since the days of the Viking missions.

"I knew people would like to go back and land on Mars, but I also knew we didn't have current advice," Rummel said.

So he assisted in the drafting of a 1992 report – Biological Contamination of Mars. The report concluded that a large part of the surface was "extremely inhospitable to terrestrial life" and for that reason, future missions would not need to be sterilized as much as the Viking missions.

But changes in landing technology meant that NASA had to be extra mindful of different scenarios for its missions. Pathfinder, for example, was supposed to fall to the surface using airbags. If the airbags failed, the mission would need to withstand a fall and possible burial in the soil of up to 1.5 meters (5 feet) without exposing possible Earth microbes to the Martian environment.

NASA has seen extensive evidence of briny water flow in recurring slope lineae, which are features that develop on the slopes of craters. Rummel, among others, speculated about recurring slope lineae as early as 2002. While researchers have long observed the formations, it was only in 2015 that NASA had strong enough evidence to say the formations are probably due to liquid water on the surface.

Rummel warned against sending Curiosity to investigate a nearby recurring slope lineae. The materials on the rover's surface could not be thoroughly sterilized with UV radiation due to their properties. And inside the rover is a warm electronics box that could melt any ice with which the box comes into contact.

RELATED: NASA Center Shows Off Sleek New Mars Rover Concept Vehicle for Astronauts

Rummel was also part of early-stage planning for a "sample return" mission to bring pieces of Mars back to Earth, in collaboration with the French space agency CNES. While that mission never went forward, NASA has left the door open for future sample return missions. The next Mars rover, called Mars 2020, is expected to leave "caches" of interesting material behind for future missions to potentially pick up and bring back to Earth, when we presumably know a little more about how to protect ourselves.

Of course, Mars wasn't the only target of note back in the 1990s when Rummel began his work. NASA already had a Jupiter probe — called Galileo — and was about to launch Cassini, which has now been orbiting Saturn since 2004. Those missions confirmed some intriguing Voyager mission results from the 1970s and 1980s, showing that some of the moons are icy and potentially habitable.

Rummel remembers modifying the planetary protection plan for Galileo as evidence emerged that a liquid ocean might lie underneath Europa's icy surface.

At the end of Galileo's mission, an option was included to deliberately crash the probe into Io or Jupiter, just in case it happened to fall into Europa, damaging a potentially habitable environment underneath the ice. Because the mission planners were uncomfortable with changing Galileo's orbit to fall into Io, they went for a Jupiter extermination — collecting science all the way down.

NASA said the job posting has generated "a lot of excitement," including from Jack Davis a fourth grader from New Jersey and self-described "Guardian of the Galaxy." In a letter to the agency, Davis said he was fit for the job because his sister thought he was an alien, among other qualifications.

Although the planetary protection officer is no intergalactic warrior, it's a position that clearly provokes the imagination of skywatchers young and old.

Originally published on Seeker.