Recurring lineae - evidence of flowing water
NASA just announced evidence for flowing water on Mars in the present. Full NASA press release now available -
The Guardian:
Liquid water runs down canyons and crater walls over the summer months on Mars, according to researchers who say the discovery raises the odds of the planet being home to some form of life.
The trickles leave long, dark stains on the Martian terrain that can reach hundreds of metres downhill in the warmer months, before they dry up in the autumn as surface temperatures drop.
Images taken from the Mars orbit show cliffs, and the steep walls of valleys and craters, streaked with summertime flows that in the most active spots combine to form intricate fan-like patterns.
Wonderful NASA Mars images
Wired:
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.
Ojha and his team have watched these lineae form every Martian summer, growing wider week after week until they slowly fade come winter—exactly the times and places where conditions are right for liquid water to exist on Mars. Plus, the surface is crusted with salt, which could help stabilize liquid water so it doesn’t boil or freeze.
Ojha notes that they haven’t actually observed water flowing on Mars. The team took their data from the CRISM instrument on the Mars Reconnaisance Orbiter, which, frustratingly, only observes the surface every day at 3 pm. That’s when Mars is at its hottest and driest, so any liquid water oozing on the surface would have long since evaporated by the time MRO laid eyes on it.
ABC's report, with some great NASA links
The Wire: Amazing photos!! Go look -
The interesting RSL resurfaced in 2014, when the orbiter turned in yet more evidence for liquid water-flows on Mars, this time observed with the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument. The press statement from the time emphasises that the MRO still hadn’t spotted direct evidence of liquid water – i.e. liquid water itself – but only surface features one of whose causes could be the flow of liquid water. In fact, it also mentions another probable cause. From 2014:
One possible explanation for these changes is a sorting of grain sizes, such as removal of fine dust from the surface, which could result from either a wet process or dry one. Two other possible explanations are an increase in the more-oxidised (ferric) component of the minerals, or an overall darkening due to moisture. Either of these would point to water, even though no water was directly detected. The spectral observations might miss the presence of water, because the [RSL] are much narrower than the area of ground sampled with each CRISM reading. Also, the orbital observations have been made only in afternoons and could miss morning moisture.
More lineae - water on Mars!
The pictures are lightboxed - click for higher resolution.