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The Planetary Society Weblog

By Emily Lakdawalla

Mars Global Surveyor Discovers Current Liquid Water Activity on Mars

Dec. 6, 2006 | 17:06 PST | Dec. 7 01:06 UTC

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There was a press conference this morning at NASA Headquarters, and it contained big news: the discovery of changes on the surface of Mars within the last few years that most likely involved liquid water flowing on the surface. I wrote up a story that's now posted here: "Mars Global Surveyor Discovers Current Liquid Water Activity on Mars."

I was trained as a scientist, not as a journalist, so I feel a bit uneasy about that headline. I think I'll reserve a healthy amount of skepticism about real liquid water flowing on Mars until someone or some instrument actually sees real liquid water actively flowing on Mars. But Malin and Edgett and friends made a very strong case at their press conference today, and their case was supported by the presence of Phil Christensen, who's not on their team and who has, in the past, published interpretations of gully features on Mars that differed from Malin's. It's certainly a strong enough case to make the Martian mid-latitudes very interesting targets for future in situ exploration, which is the main point that Christensen was on the panel to make.

One thing that I really liked about this story was how Malin and Edgett used data from every NASA orbiter (they didn't mention Mars Express at the conference, so I don't know if they used HRSC images; when I have time to read their Science article I'll look for that) to check back and look for changes. Today's story really proves how beneficial it is to have multiple orbiters in operation -- and why losing Mars Global Surveyor is a big loss even with all the rest of those orbiters in place.

The other half of the story that they presented today had to do with the discovery of 20 impact craters that have formed since Mars Global Surveyor arrived at Mars. In hindsight, it's no surprise that craters have formed since Mars Global Surveyor arrived. But there've been 240,000 images taken by MGS -- it's kind of hard to imagine how you would notice a crater that appeared in one image that hadn't appeared in previous ones. Now, it helps that fresh craters usually make very dark splotches; if you see one of those dark splotches it probably formed recently, but that could be tens, hundreds, even thousands of years ago; how would you know it could have formed just years ago? There's a neat story on how they discovered the first of these on the Malin Space Science Systems website.

Here's one of the new craters that I didn't get to include in my story, which I thought was particularly pretty:

Click to enlarge >

Fresh crater in Arabia Terra, Mars
This crater formed some time between June 30, 2002, when it was not visible in an Odyssey THEMIS image, and May 7, 2003, when it was observed in a MOC wide-angle image. This view was captured on February 26, 2006. This crater is unusual for having light-toned rather than dark-toned deposits, which indicates that the crater may have excavated lighter-toned material from beneath Mars' surface. Credit: NASA / JPL / MSSS

This unusual bright-on-dark crater reminded me of craters on Venus. And if you look at the shape of the crater, it's even got a "butterfly" pattern to its ejecta, which is very common in Venus craters but less commonly seen on Mars. If I'm right about my interpretation, the gap in the spray of ejecta to the north-northeast of the crater indicates that the impact was an oblique one (striking at a low angle to the ground), and the impactor came in from the north-northeast.

Speaking of material I didn't get to use for my story, Jim Bell gave me several more comments. Here's my favorite: "Mini-floods of water gushing across the Martian surface! How cool is that?" He went on to say, "Malin and Edgett's 'Squirting Gun' evidence for liquid water existing just below the surface of Mars -- today -- provides an enormous boost for Life on Mars advocates."

Finally, I thought I'd share with you all a statement that The Planetary Society is issuing to our press contacts on this discovery. Enjoy.

STATEMENT

The Planetary Society
65 N. Catalina Avenue, Pasadena, CA 91106-2301 (626) 793-5100 Fax (626) 793- 5528
E-mail: tps@planetary.org Web: http://planetary.org

For Immediate Release: December 6, 2006
Contact: Susan Lendroth

Planetary Society Comments on Mars Water Announcement

Today, NASA released photographs that reveal bright new deposits in two gullies on Mars, suggesting water has flowed in brief spurts on Mars within the last seven years. The Planetary Society congratulates the Mars Global Surveyor team for yet another significant scientific discovery. Below are some comments from Planetary Society Director of Projects, Bruce Betts on the significance of these findings.

Why is this important?
"If this discovery holds, it is very significant. Only a few years ago, the common belief was that liquid water last flowed on Mars over a billion years ago. Now, we see evidence that liquid water may be flowing today and may currently exist in the subsurface."

Why is it surprising that Mars would have liquid water?
"Liquid water is not stable on the Mars surface right now. It exists as an ice or a gas, like dry ice on Earth, because of the very low pressure of the Mars atmosphere."

What enabled this discovery?
"The fact that Mars Global Surveyor lasted so far beyond its projected lifetime has allowed this type of discovery that requires observing the same area over and over again."

What does this mean for the search for life on Mars?
"Liquid water is one of only three things required by all life on Earth. If there is liquid water on Mars, that makes it even more compelling to search for life on Mars. Though the chances of current microbial life on Mars are unknown, the odds may have just gone up."

What is the significance for life in the universe?
"If we did find life on Mars, our next door neighbor, that would be not only an incredibly profound discovery on its own, but also might imply that life may evolve comparatively easily, and there might be many places in the more distant universe that may harbor life."

What does this say about the significance of science missions within NASA?
"In a time when science has been under attack within the NASA budget, this once again demonstrates the importance of science missions like Mars Global Surveyor. They are missions of discovery, where the most important findings are often the most unexpected."