water flowed on Mars within last seven years

Continuing on from yesterday’s quotes from HAL as post titles, I was giddy with anticipation about NASA‘s Mars announcement today, and had to wait till I got home before the immensely satisfying statement of liquid water on Mars in the past seven years. Well there’s the balloon-puncturing ‘may have flowed’, emphasis on the scientific absence of hubris and so on, but…

“These fresh deposits suggest that at some places and times on present-day Mars, liquid water is emerging from beneath the ground and briefly flowing down the slopes. This possibility raises questions about how the water would stay melted below ground, how widespread it might be, and whether there’s a below-ground wet habitat conducive to life. Future missions may provide the answers,” said Malin.

— Science Blog


Today at 10:00 a.m. Pacific time, NASA announced they had, at long last, found strong evidence of recent liquid water flows on Mars.

Observations from the Mars Global Surveyor (MGS) have revealed “recent activity” on the surface of the red planet; recent meaning in the past seven years. These changes include cratering from impacts (which is cool enough, and I’ll blog about those later), but also, yes, the flow of water.

Years ago, there were gullies seen on slopes on Mars, and they looked a lot like water had formed them. But it was hard to tell. Now, the evidence is far stronger. For example, check out this image:

This gully is in a crater in the Centauri Montes Region in the martian southern hemisphere. The critical piece of information here is that the gully did not exist in 1999, but is clear in 2005. It’s new!

In the higher resolution images (click it to see them) you can see the gully better. You can tell by eye it certainly looks like a liquid flow.

But how do we know they are water? The context is the key. Gullies indicate the flow of a liquid. Dust avalanches do occur on Mars, but not anywhere near these gullies. The morphology (shape) is important too. See how the gully breaks up as it flows down the slope? That also indicates a fluid flow. Finally, the color is an indicator, too. The light color is difficult to make on Mars. In trenches, most places where the surface dust is disturbed, and impact craters, the underlying layers are always dark. This indicates a different process. Also, numerical calculations using models indicate that whatever caused these gullies flowed like water, not like dust or rocks.

As they say on the Malin Space Science Systems website:

Of course, water was not the only fluid considered by various colleagues; carbon dioxide can be fluid at some pressures and temperatures, and fluid carbon dioxide was also proposed as a candidate fluidizing agent. Even dry mass movement—landsliding—of unconsolidated granular material can exhibit some fluid-like behavior, and such mass movements were considered as an explanation for the gullies.

The presence of channels, primarily formed by erosion—but also displaying features representing along-channel deposition, such as levees and meanders—and terminal depositional aprons consisting of dozens to hundreds of individual flow lobes, contributed to the general acceptance of the hypothesis that gullies involved the action of liquid water.

These bright features in the gullies might be frost, but they’ve been around a while, so that’s pretty unlikely. They might be salts and other minerals deposited by the flow, or they might be smaller sediments carried along with the water.

How much water are we talking about? Maybe 5-10 swimming pools’ worth according to Ken Edgett, the scientist who has been working on these data. It would be a pretty quick flash flood, and, weirdly, in the low atmospheric pressure, the water would be boiling even at the low temperatures of Mars.

So what does this mean? Well, we’ve known of frozen water on Mars for decades, and we know there was activity in the past. These new observations indicate that things are happening on Mars now, within the past few years. And whatever it is that’s happening, it’s releasing water onto the surface, which in turn means that there is water just below the surface of Mars, at least in some places.

Sounds like a good place to build a colony, don’t you think?

It does to me. If there are big deposits of water, then that makes it a lot easier for potential colonists to survive on Mars, “living off the land”. While the amount of water in any one gully is small, it indicates more water is nearby. This is terribly exciting.

Now, the skeptic in me must say it: this is not absolute conclusive proof of water on Mars. We need better images (maybe from the new probe orbiting Mars now), and spectra would be nice (to be able to see what chemicals are there). Even better would be to land a rover near there to get samples, though gullies down the sides of crater walls would make a perilous journey for any robot.

If these aren’t water gullies, we’ll all be disappointed, but that’s science. They’ll still be interesting features! But the evidence is very, very compelling, and I certainly hope that NASA follow this up quickly with more observations.

Recent flow of water on Mars from subsurface deposits. Wow.

— Bad Astronomy Blog

Water flowed on Mars within last seven years

NASA photographs have revealed bright new deposits seen in two gullies on Mars that suggest water carried sediment through them sometime during the past seven years.

“These observations give the strongest evidence to date that water still flows occasionally on the surface of Mars,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program, Washington.

Liquid water, as opposed to the water ice and water vapor known to exist at Mars, is considered necessary for life. The new findings heighten intrigue about the potential for microbial life on Mars. The Mars Orbiter Camera on NASA’s Mars Global Surveyor provided the new evidence of the deposits in images taken in 2004 and 2005.

“The shapes of these deposits are what you would expect to see if the material were carried by flowing water,” said Michael Malin of Malin Space Science Systems, San Diego. “They have finger-like branches at the downhill end and easily diverted around small obstacles.” Malin is principal investigator for the camera and lead author of a report about the findings published in the journal Science.

The atmosphere of Mars is so thin and the temperature so cold that liquid water cannot persist at the surface. It would rapidly evaporate or freeze. Researchers propose that water could remain liquid long enough, after breaking out from an underground source, to carry debris downslope before totally freezing. The two fresh deposits are each several hundred meters or yards long.

The light tone of the deposits could be from surface frost continuously replenished by ice within the body of the deposit. Another possibility is a salty crust, which would be a sign of water’s effects in concentrating the salts. If the deposits had resulted from dry dust slipping down the slope, they would likely be dark, based on the dark tones of dust freshly disturbed by rover tracks, dust devils and fresh craters on Mars.

Mars Global Surveyor has discovered tens of thousands of gullies on slopes inside craters and other depressions on Mars. Most gullies are at latitudes of 30 degrees or higher. Malin and his team first reported the discovery of the gullies in 2000. To look for changes that might indicate present-day flow of water, his camera team repeatedly imaged hundreds of the sites. One pair of images showed a gully that appeared after mid-2002. That site was on a sand dune, and the gully-cutting process was interpreted as a dry flow of sand.

Today’s announcement is the first to reveal newly deposited material apparently carried by fluids after earlier imaging of the same gullies. The two sites are inside craters in the Terra Sirenum and the Centauri Montes regions of southern Mars.

“These fresh deposits suggest that at some places and times on present-day Mars, liquid water is emerging from beneath the ground and briefly flowing down the slopes. This possibility raises questions about how the water would stay melted below ground, how widespread it might be, and whether there’s a below-ground wet habitat conducive to life. Future missions may provide the answers,” said Malin.

Besides looking for changes in gullies, the orbiter’s camera team assessed the rate at which new impact craters appear. The camera photographed approximately 98 percent of Mars in 1999 and approximately 30 percent of the planet was photographed again in 2006. The newer images show 20 fresh impact craters, ranging in diameter from 7 feet (2 meters) to 486 feet (148 meters) that were not present approximately seven years earlier. These results have important implications for determining the ages of features on the surface of Mars. These results also approximately match predictions and imply that Martian terrain with few craters is truly young.

Mars Global Surveyor began orbiting Mars in 1997. The spacecraft is responsible for many important discoveries. NASA has not heard from the spacecraft since early November. Attempts to contact it continue. Its unprecedented longevity has allowed monitoring Mars for over several years past its projected lifetime.


— Science Blog