Is there really water on Mars?

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Introduction to Is there really water on Mars?

When scientists compared high-resolution 3-D images of Mars taken in 2005 to those taken in 1999, they noticed something unusual. A series of bright, depositary streaks had formed in gullies during the intervening years. Since flash floods can carve away soil and leave behind new sediments on Earth, some observers believed they finally had strong evidence that liquid water, and therefore the potential for life, existed on Mars.

Mars Image Gallery

Image courtesy NASA/JPL/
University of Arizona
The Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE) camera took captured images of gully
channels on Mars. See more Mars pictures.

Since life as we know it -- even the most bizarre or minute varieties of life -- depends on liquid water, scientists assume that it would also be a necessity for extraterrestrial organisms. Mars is replete with water, but most (if not all) of it is in frozen or vapor form. Ice caps the planet's poles and might also circle areas near the equator [source: The New York Times]. Patches of ice lie over dunes in craters. Mars also shows signs of having had liquid water in the past. Studies of craters like the Holden crater show erosion patterns suggestive of ancient Martian rain.

But until recently, most people assumed that if Mars had liquid water, it no longer did and hadn't for quite some time. Just a decade ago, scientists speculated that the planet hadn't had liquid water for several billion years. The atmosphere and temperature of Mars makes the idea of liquid water -- or at least water as we know it -- seem nearly impossible. The planet is extremely dry and its distance from the sun keeps the temperature between 22 and -124 degrees Fahrenheit (5.5 and -86.6 degrees Celsius).

However, liquid water on Mars wouldn't necessarily be the same as liquid water on Earth. If the water was highly acidic, for example, it would have a lower freezing point and could maintain its liquid state in the chilly climate [source: National Geographic].

But where would liquid Martian water come from? What else could have caused the depository streaks? Go to the next section to find out.

The Mars Reconnaissance Orbiter

Image courtesy NASA Jet Propulsion Laboratory (NASA-JPL)
The Mars Reconnaissance Orbiter keeps an eye out for evidence of life on Mars.

While the sudden appearance of depository streaks thrilled many scientists, others began to question the flash-flood theory. Further analysis of at least one of the gullies suggested that its shape didn't match up with the way fast-moving water flows. The deposits' finger-like shape suggested something granular and dry rushed through the valley -- like fine-grained sand [source: National Geographic].

However, this doesn't completely discount the possibility that there was liquid water involved. Even if the gullies were carved by sand, wet conditions could've initiated the landslide or a small amount of water could've mixed with dirt and sand to form slurry [source: National Geographic].

The images that got scientists speculating came from the High Resolution Imaging Science Experiment (HiRISE), an instrument that can capture minute landscape details and geologic structures. It's one of six instruments that make up the Mars Reconnaissance Orbiter. The orbiter was launched in 2005 to determine if there was ever life on Mars. While scientists hope the mission will also clarify the climate and geology of the planet, the orbiter's scientific payload focuses on the detection of water.

The orbiter's cameras and spectrometers search for mineral deposits left by water. A sounder uses radar to find underground liquid reserves. Other cameras monitor clouds and dust storms. All of the information from the Mars Reconnaissance Orbiter is relayed back to Earth through X-band and Ka-band radio waves that are picked up by the Deep Space Network antenna in Canberra, Australia.

Why water?
We tend to take water's properties for granted, but it's an unusual compound. Most planetary scientists agree: Liquid water is necessary for life. But why? The powerful solvent is able to dissolve molecules easily allowing nutrients and metabolites to circulate.

But while the orbiter's primary mission is to see if life ever existed on Mars -- a goal the presence of liquid water would strongly support -- it has a secondary agenda as well. The orbiter's high-resolution cameras create a record of Mars' rocky terrain. This information could help future manned missions know which spots are safe for landing, paving the way to human exploration of the red planet.

To learn more about Mars, the Mars Odyssey and water, explore the links on the next page.

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Is there really water on Mars?