Chelsea Leu’s Wired article was the first to appear in my RSS feed, describing the discovery of water on that world.
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.
CBC went into more detail about the potential implications of this water for life and its sources.
[The team] added that on Earth, similar brines offer “the only known refuge for active microbial communities” in the driest parts of Chile’s Atacama Desert.
On Mars, such brines could provide “transiently wet conditions near surface,” the researchers said. However, they cautioned that the amount of water may be too low to support known organisms that exist on Earth.
The researchers said they still don’t know where the water might be coming from – it’s probably not from melting ice, since the streaks are found near Mars’s equator, where it’s unlikely there could be any ice near the surface.
It could be coming directly from the atmosphere, but researchers aren’t sure if there’s enough water vapour in Mars’s atmosphere for that to happen. They might also come from a local aquifer, but since aquifers tend to be low-lying, that doesn’t explain why some of the streaks extend all the way up to the tops of local peaks. They suggested that the water source might be different for different slope lineae.
Even this discovery still means that Mars is a profoundly inhospitable world. The recent discovery of perchlorates underlines this issue. It does make it a bit less inhospitable, a less sere world.