Moons of Confusion: Why Finding Extraterrestrial Life may be Harder than we Thought

Sunday, October 19, 2014

Moons of Confusion: Why Finding Extraterrestrial Life may be Harder than we Thought

Moons of Confusion: Why Finding Extraterrestrial Life may be Harder than we Thought:

NASA’s James Webb Space Telescope, scheduled for launch in 2018, will be capable of measuring the spectrum of the atmospheres of Earthlike exoplanets orbiting small stars.
Credit: NASA, Northrop Grumman

Astronomers and planetary scientists thought they knew how to find evidence of life on planets beyond our Solar System. But, a new study indicates that the moons of extrasolar planets may produce “false positives” adding an inconvenient element of uncertainty to the search.

More than 1,800 exoplanets have been confirmed to exist so far, with the count rising rapidly. About 20 of these are deemed potentially habitable. This is because they are only somewhat more massive than Earth, and orbit their parent stars at distances that might allow liquid water to exist.

Astronomers soon hope to be able to determine the composition of the atmospheres of such promising alien worlds. They can do this by analyzing the spectrum of light absorbed by them. For Earth-like worlds circling small stars, this challenging feat can be accomplished using NASA’s James Webb Space Telescope, scheduled for launch in 2018.

They thought they knew how to look for the signature of life. There are certain gases which shouldn’t exist together in an atmosphere that is in chemical equilibrium. Earth’s atmosphere contains lots of oxygen and trace amounts of methane. Oxygen shouldn’t exist in a stable atmosphere. As anyone with rust spots on their car knows, it has a strong tendency to combine chemically with many other substances. Methane shouldn’t exist in the presence of oxygen. When mixed, the two gases quickly react to form carbon dioxide and water. Without some process to replace it, methane would be gone from our air in a decade.

On Earth, both oxygen and methane remain present together because the supply is constantly replenished by living things. Bacteria and plants harvest the energy of sunlight in the process of photosynthesis. As part of this process water molecules are broken into hydrogen and oxygen, releasing free oxygen as a waste product. About half of the methane in Earth’s atmosphere comes from bacteria. The rest is from human activities, including the growing of rice, the burning of biomass, and the flatulence produced by the vast herds of cows and other ruminants maintained by our species.

By itself, finding methane in a planet’s atmosphere isn’t surprising. Many purely chemical processes can make it, and it is abundant in the atmospheres of the gas giant planets Jupiter, Saturn, Uranus, and Neptune, and on Saturn’s large moon Titan. Although oxygen alone is sometimes touted as a possible biomarker; its presence, by itself, isn’t rock solid evidence of life either. There are purely chemical processes that might make it on an alien planet, and we don’t yet know how to rule them out. Finding these two gases together, though, seems as close as one could get to “smoking gun” evidence for the activities of life.

A monkey wrench was thrown into this whole argument by an international team of investigators led by Dr. Hanno Rein of the Department of Environmental and Physical Sciences at the University of Toronto in Canada. Their results were published in the May, 2014 edition of the Proceedings of the National Academy of Sciences USA.

Suppose, they posited, that oxygen is present in the atmosphere of a planet, and methane is present separately in the atmosphere of a moon orbiting the planet. The team used a mathematical model to predict the light spectrum that might be measured by a space telescope near Earth for plausible planet-moon pairs. They found that the resulting spectra closely mimicked that of a single object whose atmosphere contained both gasses.

Unless the planet orbits one of the very nearest stars, they showed it wasn’t possible to distinguish a planet-moon pair from a single object using technology that will be available anytime soon. The team termed their results “inconvenient, but unavoidable…It will be possible to obtain suggestive clues indicative of possible inhabitation, but ruling out alternative explanations of these clues will probably be impossible for the foreseeable future.”

References and further reading:

The Habitable Exoplanets Catalog, Planetary Habitability Laboratory, University of Puerto Rico at Arecibo

Kaltenegger L., Selsis F., Fridlund M. et al. (2010) Deciphering spectral fingerprints of habitable exoplanets. Astrobiology, 10(1) p. 89-102.

Major J. (2013) Earthlike exoplanets are all around us. Universe Today

Rein H., Fujii Y., and Spiegel D. S. (2014) Some inconvenient truths about biosignatures involving two chemical species on Earth-like exoplanets. Proceedings of the National Academy of Sciences, 111(19) p. 6871-6875.

Sagan C., Thompson W. R., Carlson R., Gurnett, D., Hord, C. (1993) A search for life on Earth from the Galileo spacecraft. Nature, 365 p. 715-721.

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NASA Photos Photography

The National Aeronautics and Space Administration (NASA) is the United States government agency responsible for the civilian space program as well as aeronautics and aerospace research. President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA's predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

UFO SIGHTINGS PHOTO PHOTOGRAPHY

The Oxford English Dictionary defines a UFO as "An unidentified flying object; a 'flying saucer'." The first published book to use the word was authored by Donald E. Keyhoe. The acronym "UFO" was coined by Captain Edward J. Ruppelt, who headed Project Blue Book, then the USAF's official investigation of UFOs. He wrote, "Obviously the term 'flying saucer' is misleading when applied to objects of every conceivable shape and performance. For this reason the military prefers the more general, if less colorful, name: unidentified flying objects. UFO (pronounced Yoo-foe) for short." Other phrases that were used officially and that predate the UFO acronym include "flying flapjack", "flying disc", "unexplained flying discs", "unidentifiable object", and "flying saucer". The phrase "flying saucer" had gained widespread attention after the summer of 1947. On June 24, a civilian pilot named Kenneth Arnold reported seeing nine objects flying in formation near Mount Rainier. Arnold timed the sighting and estimated the speed of discs to be over 1,200 mph (1,931 km/h). At the time, he described the objects' shape as being somewhat disc-like or saucer-like, leading to newspaper accounts of "flying saucers" and "flying discs". In popular usage the term UFO came to be used to refer to claims of alien spacecraft. and because of the public and media ridicule associated with the topic, some investigators prefer to use such terms as unidentified aerial phenomenon (or UAP) or anomalous phenomena, as in the title of the National Aviation Reporting Center on Anomalous Phenomena (NARCAP).

UFO PHOTO PHOTOGRAPHY

UFO - Unidentified Flying Object An unidentified flying object, or UFO, in its most general definition, is any apparent anomaly in the sky that is not identifiable as a known object or phenomenon. Culturally, UFOs are associated with claims of visitation by extraterrestrial life or government-related conspiracy theories, and have become popular subjects in fiction. While UFOs are often later identified, sometimes identification may not be possible owing to the usually low quality of evidence related to UFO sightings (generally anecdotal evidence and eyewitness accounts). Stories of fantastical celestial apparitions have been told since antiquity, but the term "UFO" (or "UFOB") was officially created in 1953 by the United States Air Force (USAF) to serve as a catch-all for all such reports. In its initial definition, the USAF stated that a "UFOB" was "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." Accordingly, the term was initially restricted to that fraction of cases which remained unidentified after investigation, as the USAF was interested in potential national security reasons and/or "technical aspects" (see Air Force Regulation 200-2). During the late 1940s and through the 1950s, UFOs were often referred to popularly as "flying saucers" or "flying discs". The term UFO became more widespread during the 1950s, at first in technical literature, but later in popular use. UFOs garnered considerable interest during the Cold War, an era associated with a heightened concern for national security. Various studies have concluded that the phenomenon does not represent a threat to national security nor does it contain anything worthy of scientific pursuit (e.g., 1951 Flying Saucer Working Party, 1953 CIA Robertson Panel, USAF Project Blue Book, Condon Committee).

Photos of Nature | Nature Photography What is The Universe

Photos of Nature | Nature Photography What is The Universe

Sunday, October 19, 2014