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CoolHand writes:

NASA Discovers Evidence for Liquid Water on Mars

For years, scientists have known that Mars has ice locked away within its rusty exterior. More elusive, though, is figuring out how much of that water is actually sloshing around in liquid form. Now, NASA scientists have found compelling evidence that liquid water—life-giving, gloriously wet H20—exists on Mars.

We're not talking gushing rivers or oceans here. These scientists have been investigating "recurring slope lineae," patches of precipitated salt that appear to dribble down Mars' steep slopes like tears rolling gently down a cheek. Planetary scientists hypothesized that the streaky formations were products of the flow of water, but they didn't have concrete, mineralogical evidence for that idea until now, says Lujendra Ojha, a scientist at Georgia Tech who first spotted the lineae back in 2010. In a new Nature Geoscience paper, published online today, Ojha and his colleagues present "smoking gun validation" that it was liquid water flowing on Mars' surface that formed these tear stains.

gman003 writes:

NASA reports strong evidence that liquid water exists on Mars at the present time.

Spectrographic readings from the Mars Reconnaissance Orbiter indicate the presence of hydrated salts, mostly perchlorates, in a common surface feature called "recurring slope lineae". The best conclusion at this time is that, during the summer months, salty water melts and flows downhill to form the lineae, then freezes during the winter.

This water may, however, be unable to support life. The salt content is incredibly high, which lowers the freezing point and allows it to melt at -23° Celsius. An Antarctic lake with similarly low temperature and high salinity is lifeless, so scientists are conservative in stating the effects this has on the potential for life on Mars.

RSLs have long been considered weak evidence for water on Mars. Current Mars rovers are prohibited from examining them, as they were not sufficiently sanitized before launch, and Earth microbes may have hitched a ride. While the Mars 2020 mission will also not be completely sterilized, I expect probes after that will be, to examine these formations up close.

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takyon writes:

An experiment using simulated Martian conditions has found that perchlorates bathed in UV light would quickly kill many potential Martian bacteria:

The hope for Martian life took another blow today. As Ian Sample at The Guardian reports, a new study suggests that in the presence of ultraviolet light, perchlorates, a class of chemical compounds widespread on Mars' surface, turn deadly for bacteria.

The presence of perchlorates isn't new. Viking 1 and 2 spacecraft detected perchlorates when they landed on the Martian surface in 1976, Jeffrey Kluger reports for Time. Since then, other spacecraft have confirmed the presence of the compounds. The 2009 Phoenix lander found that perchlorates make up between 0.4 and 0.6 percent of the soil sample it collected.

While perchlorates, which are composed of chlorine and oxygen, are toxic to humans, microbes typically love the stuff. And researchers have been optimistic that their presence could support bacterial life on Mars. As Kluger reports, some bacteria on Earth use naturally occurring perchlorate as an energy source. The compound also lowers the melting point of water, which could improve the chance of liquid water existing on the Red Planet.

But the latest study, published in the journal Scientific Reports [open, DOI: 10.1038/s41598-017-04910-3] [DX], suggests that in the presence of ultraviolet light perchlorate is not so microbe-friendly. Mars has a thin atmosphere, which often leaves its surface bathed in UV rays. And when heated, chlorine-based molecules like perchlorates cause heavy damage to living cells, reports Sarah Fecht at Popular Science.

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Thexalon writes:

NASA's Curiosity rover has discovered ancient organic molecules on Mars. That plus the methane is strongly suggesting that life may have existed on Mars back when liquid water existed on the surface.

NASA's Curiosity rover has found new evidence preserved in rocks on Mars that suggests the planet could have supported ancient life, as well as new evidence in the Martian atmosphere that relates to the search for current life on the Red Planet. While not necessarily evidence of life itself, these findings are a good sign for future missions exploring the planet's surface and subsurface.

The new findings – "tough" organic molecules in three-billion-year-old sedimentary rocks near the surface, as well as seasonal variations in the levels of methane in the atmosphere – appear in the June 8 edition of the journal Science.

Organic molecules contain carbon and hydrogen, and also may include oxygen, nitrogen and other elements. While commonly associated with life, organic molecules also can be created by non-biological processes and are not necessarily indicators of life.

"With these new findings, Mars is telling us to stay the course and keep searching for evidence of life," said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters, in Washington. "I'm confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet."

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takyon writes:

Organic Matter on Dwarf Planet Ceres More Abundant than Thought

A new analysis of data collected by NASA's Dawn orbiter suggests that organic molecules may exist in surprisingly high concentrations on the surface of Ceres. The study [DOI: 10.1029/2018GL077913] [DX] appears in the journal Geophysical Research Letters.

[...] To get an initial idea of how abundant those compounds might be, researchers compared the [Visible and Infrared Spectrometer] data from Ceres with lab reflectance spectra of organic material formed on Earth. Based on that standard, they concluded that 6-10% of the spectral signature they detected on Ceres could be explained by organic matter.

But for this the new study, Southwest Research Institute researcher Hannah Kaplan and co-authors wanted to re-examine those data using a different standard. Instead of relying on Earth rocks to interpret the data, they turned to an extraterrestrial source: meteorites. Some meteorites have been shown to contain organic material that's slightly different from what's commonly found on our own planet. And the new analysis shows that the spectral reflectance of the extraterrestrial organics is distinct from that of terrestrial counterparts. [...] "We estimate that as much as 40-50% of the spectral signal we see on Ceres is explained by organics. That's a huge difference compared to the 6-10% previously reported based on terrestrial organic compounds."

[...] There are two competing possibilities for where Ceres' organics may have come from. They could have been produced internally on Ceres and then exposed on the surface, or they could have been delivered to the surface by an impact from an organic-rich comet or asteroid.

Previously: Organic Molecules Found on Ceres

Related: Dawn Spies Magnesium Sulphate and Possible Geological Activity on Ceres
Ceres May Have Had a Global Surface Ocean in the Past

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takyon writes:

Saturn moon a step closer to hosting life

Scientists have found complex carbon-based molecules in the waters of Saturn's moon Enceladus.

Compounds like this have only previously been found on Earth, and in some meteorites. They are thought to have formed in reactions between water and warm rock at the base of the moon's subsurface ocean.

Though not a sign of life, their presence suggests Enceladus could play host to living organisms. The discovery came from data gathered by the Cassini spacecraft.

Also at SwRI, ScienceAlert, Space.com, National Geographic, Popular Mechanics, and The Guardian.

Macromolecular organic compounds from the depths of Enceladus (DOI: 10.1038/s41586-018-0246-4) (DX)

Related: Minerals In Plumes of Enceladus Indicate Hydrothermal Activity
Hydrogen Emitted by Enceladus, More Evidence of Plumes at Europa
Could a Dedicated Mission to Enceladus Detect Microbial Life There?
How the Cassini Mission Led a 'Paradigm Shift' in Search for Alien Life
Cassini Spacecraft Post-Mortem
Porous Core Could be Keeping Enceladus Warm
Yuri Milner Considering Privately Funded Mission to Enceladus
Organic Molecules Found on Ceres
NASA Finds Evidence of Water Plume on Europa
Organic Matter Found on Mars
Study Finds Evidence of More Organic Material on Ceres

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