Washington, DC -- In what could turn out to be a landmark discovery in the history of Mars exploration, imaging scientists using data from NASA's Mars Global Surveyor spacecraft have recently observed features that suggest there may be current sources of liquid water at or near the surface of the red planet.
The new images show the smallest features ever observed from martian orbit -- the size of an SUV. NASA scientists compare the features to those left by flash floods on Earth.
"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 groundwater supply, similar to an aquifer," said Dr. Michael Malin, principal investigator for the Mars Orbiter Camera on the Mars Global Surveyor spacecraft at Malin Space Science Systems (MSSS), San Diego, CA. "These are new landforms that have never been seen before on Mars." The findings will be published in the June 30 issue of Science magazine .
The Mariner 9 spacecraft in 1972 found evidence that billions of years ago the planet had water on its surface. The new pictures from Global Surveyor may show where the water went.
The gullies in the images are on cliffs such as in crater or valley walls and are made up of a deep channel with a collapsed region at its upper end and an area of accumulated debris that appears to have been transported down the slope. The gullies appear to be extremely young, meaning they may have formed in the recent past.
"They could be a few million years old, but we cannot rule out that some of them are so recent as to have formed yesterday," Malin said.
Because the atmospheric pressure at the surface of Mars is about 100 times less than it is at sea level on Earth, liquid water would immediately begin to boil when exposed at the martian surface. Investigators believe that this boiling would be violent and explosive. So how can these gullies form? Malin explained that the process must involve repeated outbursts of water and debris, similar to flash floods on Earth.
"We've come up with a model to explain these features and why the water would flow down the gullies instead of just boiling off the surface. When water evaporates it cools the ground -- that would cause the water behind the initial seepage site to freeze.
This would result in pressure building up behind an 'ice dam.' Ultimately, the dam would break and send a flood down the gully," said Edgett.
The occurrence of gullies, mostly in the martian southern hemisphere, is quite rare: only a few hundred locations have been seen in the many tens of thousands of places surveyed by the orbiter camera.
The water supply is believed to be about 100 to 400 meters (300 to 1,300 feet) below the surface, and limited to specific regions across the planet. Each flow that came down each gully may have had a volume of water of about 90,000 cubic feet, about enough water to sustain 100 average households for a month.
"This latest discovery by the Mars Global Surveyor is a true 'watershed'--that is, a revolution that pushes the history of water on Mars into the present," said Dr. Jim Garvin, Mars Program Scientist, NASA Headquarters.
To follow up on the discovery, Garvin said, NASA will continue to search with Mars Global Surveyor and its remote sensing instruments, and in 2001, NASA will launch a scientific orbiter with a high spatial resolution middle-infrared imaging system that will examine the seepage sites in search of evidence of water-related minerals. NASA may also plan a 2003 mission to Mars.
JPL manages the Mars Global Surveyor Mission for NASA's Office of Space Science, Washington, DC. Malin Space Science Systems built and operates the camera system. JPL is a division of the California Institute of Technology, Pasadena, CA. JPL's industrial partner is Lockheed Martin Astronautics, Denver, CO, which developed and operates the spacecraft.
To see more images, visit Malin Space Science Systems' site.
