Water On Mars

The existence of water on Mars has been a hot topic of discussion for almost three hundred years. Recently it has resurfaced due to the findings of NASA’s Mars Global Surveyor. The first evidence that there was water on Mars was found in 1813 when astronomers noticed that the polar caps of Mars were shrinking. Mars has poles similar to the North and South poles seen on Earth. Mars also goes through a changing of seasons much like the Earth does. The combination of these two things would indicate that Mars should have water on it. In 1813 this belief was a good one based on the tools they had at the time. Since the poles were shrinking they must have been melting, thus producing water. The next signal that there was water on Mars occurred in 1877 when Giovanni Schiaparelli observed channels on Mars. The problem with this observation was that he called these features “canali” which translates in English to “canal.” Canals, of course, refer to artificially built waterway systems. This became bad because everybody looked for Martians. Schiaparelli’s observations were actually very correct as described by Dr. Ken Edgett, staff scientist at MSSS, “Twenty-eight years ago the Mariner 9 spacecraft found evidence- in the form of channels and valleys- that billions of years ago the planet had water flowing across its surface.”[1] These channels were placed into two groups: runoff channels and outflow channels (as seen in figures 1 and 2). The runoff channels are best described by comparing them to tributary systems seen on Earth. The channels are in a fan-shaped system, which are all fed from the same source. But, the question is where did the water come from to feed these runoff channels? Some speculate it was from rainfall, while others believe it came from underground. Outflow channels, on the other hand, have few tributaries. Outflow channels are consistently deeper and wider than runoff channels. These channels are huge and one of the biggest is Ares Vallies. Experts believe that catastrophic flooding was the cause of these outflow channels. So, when were these channels formed? Most say they were formed about 3.5 to 4 billion years ago, before the volcanic plains were formed by the flow of lava. The two questions always being debated were: 1) Was there ever water at all on Mars? 2) If so, where did all the water go?

Today, scientists feel quite certain about the answers to these age-old questions. Through numerous missions, especially that of the Mars Global Surveyor, it has been unanimously agreed upon that a great deal of water did exist on Mars at one time and still does to this day. Also through such missions, areas where water may be held inside Mars have been discovered: these areas are known as gullies.

The mission of the Mars Global Surveyor found evidence pointing towards water seepage on Mars’s craters in the recent past and possible even today. The evidence is based upon some stream-like features and fan-shaped deposits that show similar resemblance to those of the Earth. The principle investigator for the Mars Orbiter Camera on the mission was heard giving this statement:

We see features that look like gullies formed by flowing water and the deposits of soil and rocks transported by these flows. The features appear to be so young that they might be forming today. We think we are seeing evidence of a ground water supply, similar to an aquifer. These are new landforms that have never been seen before on Mars. [2]

Due to some of the new pictures brought to us from the Global Surveyor, we now know that some of the water from the planet’s beginning went under ground and is quite possibly still there. Going along with this theory is Laurie Leshin’s recent discovery. Her studies suggest that the crust of Mars is holding at least two to three times as much water as previously believed by former scientists. The study makes reference to the idea that Mars has lost much less water over its lifetime than previously predicted. Leshin came to such a conclusion by comparing the amount of deuterium in Mar’s atmosphere water to that of a meteorite that was thrown from Mar’s atmosphere three million years ago and was recently discovered in Antarctica in 1994. (Figure 3) Her findings were a surprise. They showed that the water bearing crystals in the meteorite were much more rich in deuterium than expected. This meant that the level was similar to that of the water on Mars today with its present atmosphere. Leshin stated, “They are more similar than we thought they were, although they are still different. It’s the size of the difference between the two that’s less than previously thought.” [3] So, as stated earlier, when added together this discovery means that Mars has held on to two to three times the amount of water than had previously been thought until now.

As far as where the water is surfacing, one looks to formations known as gullies. These gullies appear to be on cliffs in craters or on valley walls, and are made up of an alcove and an apron. An alcove is a deep channel with a collapsed region at its upper end, and an apron is an area of accumulated debris at the other end of the alcove. These formations (gullies) appear to be extremely young having formed in the recent past; some possibly could even have formed as recently as yesterday. (Refer back to Figure 2) Many wonder exactly how these gullies have formed because the atmospheric pressure at the surface of Mars is around 100 times less than it is at sea level on Earth, and the liquid water would immediately start to boil when exposed to the Martian surface. To explain this, the process has to include repeated outbursts of both water and debris over time, like that of flash floods on the Earth. There is a model that helps explain the features of the gullies and why the water flows down the gullies instead of just boiling off at the surface. The model explains that as water evaporates the ground is cooled, which in turn causes water behind the initial seepage to freeze up. Once this occurs, there would be a pressure build up behind the “ice dam.” In the end the dam would break sending a flood down the gully. The interesting aspect of these gullies is that they occur in areas that are not expected and seem to defy common sense and what we know about the stability of water. Not only do they occur in the coldest regions of the planet, but they are located on slopes that face away from the sun, where temperature only reaches about minus 50 degrees Centigrade, and the water seems to be seeping out from an area right below the surface, which was previously believed to be frozen. So, scientists do still have to figure out this phenomenon.

For the future, NASA is looking to send out a new orbiter in 2001 to Mars, which will have a higher resolution spectrometer to search for carbonates, which until now have yet to be found. Then in 2003, NASA plans to send out two “rovers” to Mars in search of water’s signatures in rocks and soil on Mars’s surface. The reason for such missions is that scientists feel that they have to have samples from Mar’s in order to answer those questions that still remain to be unanswered at this point.

[1] www.spacescience.com, “Mars Surprise,” June 22, 2000

[2] www.spacescience.com, “Mars Surprise,” June 22, 2000

[3] www.space.com, “Mars Hides Much More Water, Study Suggests”, June 28, 2000

http://seds.lpl.Arizona.edu/nineplanets/mars.html, 3/5/96
http://www.space.com, “Mars Hides Much More Water, Study Suggests”, June 28, 2000
http://www.space.com/scienceastronomy/solarsystem/mars_hiding_000628.html
http://www.spacescience.com/headlines/y2000/ast22jun_2.htm?list
http://www.spacescience.com, “Mars Surprise,” June 22, 2000