This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Astrobiology has one key advantage when it comes to tooting its own horn - it can lay claim to a diverse range of scientific research as being relevant to the study of life in the universe.
In that spirit (and an optimistic celebration of what might, just possibly, hopefully, be the advent of spring-like conditions in the eastern half of the United States), here's a small blizzard of new results:
Dawn makes it to Ceres—In a feat of mind-bending orbital dynamics (see also the movie below) NASA's Dawn mission has made it to a capture state around the dwarf planet Ceres. From here it will descend to its full science orbit — a circular polar loop around Ceres that takes the spacecraft to about 8,400 miles off the surface of this fascinating body and allows it to map the surface tip to tail, starting April 23rd, 2015. Does Ceres have a rich water-ice content? Did it ever have a subsurface, potentially life-harboring ocean? What are the bright spots that Dawn has already seen? With any luck all will be revealed...
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Wet Mars?—A new study with Earth-based telescopes has peered at the isotopic composition of atmospheric water on Mars. It finds that above the polar regions there is a 7-fold enhancement of deuterated water (where the heavy hydrogen isotope deuterium forms DHO molecules rather than the lighter H2O molecules). This indicates that the polar ice itself must be 8 times more deuterated than Earth's ocean water.
The reason? The heavier DHO molecules get preferentially left behind when water is lost to space through a planetary atmosphere. To reach this observed concentration a lot of water must have been lost in the past - enough in fact to cover 19 percenet of Mars with a bona fide ocean in the Northern Plains that could have been as deep as 1.6 kilometers some 3.7-4.5 billion years ago.
GJ 581d, now you see it, now you don't, now you do—Exoplanets down at the scale of the Earth are hugely difficult to detect, they're right at the hairy edge of what current astronomical technology is capable of. The putative planet GJ 581d - a possible 'super-Earth' in the habitable zone of its parent star - has had a checkered and contentious history. It first popped up in 2009, but in 2014 it 'went away' as researchers claimed that it was a case of stellar noise masquerding as a planet signal. The GJ 581 system has had its share of controversy over other planets too. But now a new study is claiming that 581d is indeed real...and naturally there is a response that says it's still just stellar noise. Time will tell.
Life in liquid methane—The surface environment on Titan is a wee bit chilly, with an average temperature of about 94 Kelvin (a lovely -290F). But with a roughly Earth-like atmospheric pressure it's pretty much perfect for a substance like methane to exist as a liquid (below 112 Kelvin or -259F at 1 atmosphere pressure). And indeed, Titan is awash with methane lakes and methane rain.
Could life exist here? It's a good question. To operate in any analogous way to life as we understand it, such conditions demand that an organism would need to substitute the wonderful solvent of water with something else - perhaps methane (although it's a non-polar solvent).
An interesting theoretical study has come up with what could be one part of the solution - an organic nitrogen compound, acrylonitrile azotosome - capable of forming flexible membrane structures that could serve as cell walls in these conditions. There's a lot more to figure out, like what a Titanian organism's metabolism might be, but earlier speculations about a hydrogen-acetylene food source might not be so outlandish after all...
