Big news from the NASA Mars team today. There is now strong evidence of at least occasional surface water on Mars! This is especially exciting in light of recent reinterpretation of old evidence that has lead scientists to believe that Mars contains organic molecules.
Let that sink in for a minute. We now know that Mars has both water and organic molecules!
For a detailed analysis of the new information, see The Visionlearning Blog, where staff writer David Warmflash landed an inside scoop and broke the story this morning. The new data are revealed in a paper by Lujendra Ojha and colleagues published today in the journal Nature Geoscience.
The idea of water on the surface of Mars is an old one. Astronomers in the 1800s saw black lines on the Martian surface and thought they could be rivers or even canals constructed by intelligent life forms. However, it has been known for many decades that Mars has an extremely thin atmosphere and so there is negligible atmospheric pressure on the surface. This means that water evaporates far more quickly than it does on Earth. No pressure; no water. By the 1970s, photographs from space probes confirmed that the black lines do not contain running water.
However, new data has confirmed something has been speculated previously: the Martian surface has a great abundance of an ion called perchlorate.
So what, you ask? The presence of perchlorate changes the story because if water ever emerged on the surface of Mars, say from an underground reservoir, it would have a high concentration of dissolved perchlorate and be extremely salty. Very salty water has different properties. For starters, it does not vaporize nearly as easily, even at low atmospheric pressure. In other words, the presence of perchlorate means that water would persist on the surface much longer than previously thought.
If water did persist for extended periods of time on the Martian surface, it would collect into steams and flow down hills and mountains, just like bodies of water on Earth. Over time, flowing creeks and rivers would cut lines into the surface of Mars, which would remain visible even after the river ran dry. Those black streaks on Mars may be the scars left by dried up rivers. If they are, we would expect an even higher concentration of perchlorate within the black lines, as salt left behind from the evaporating rivers.
That is exactly what Ojha and colleagues found! The high concentration of perchlorate within the black streaks on Mars is strong evidence that water has flowed on Mars in the recent past. This argues that there must be sub-surface sources of liquid water. While the surface water would be far too salty to support life as we currently understand it, the hidden sources of water could be very different. There could be small lakes or even vast oceans of liquid water under the surface. Protected from the temperature extremes and harsh solar radiation on the surface, who knows what interesting things are lurking?!
The other big implication of the confirmation of abundant perchlorate on Mars is that it may tell us that there are organic molecules on Mars after all. The only organic molecules found by the Viking missions in the 1970s and 80s were trace amounts of chloromethane and dichloromethane. Since these are both common compounds in industrial cleaners, scientists assumed these were contaminants brought by the Viking landers themselves.
However, once again, the presence of perchlorate on the surface of Mars changes this interpretation also. When organic compounds are treated with perchlorate, among the most common products are chloromethane and dichloromethane. This means that the organic compounds that the Viking landers detected all those years ago may have been Martian in origin after all!
The issue of water and organics on Mars will be explored and debated by the scientific for years to come, but there is no denying that the search for life on Mars just got a huge boost.
Nathan H. Lents (@nathanlents)
