mars_flow_020220 A team of researchers studying photographs of Mars has found teardrop features that they say were sculpted by flowing water as recently as 10 million years ago.
Evidence for water-carved channels on the Red Planet dates back to the 1970s Viking missions. More recently, the orbiting Mars Global Surveyor (MGS) probe has provided pictures that reveal what may be ancient river beds and sedimentary layers associated with lakes or oceans. Controversial evidence has emerged indicating more recent bursts of water flowing down ravines and crater walls.
The newest study involves MGS images studied by scientists at NASA and the University of Arizona. The researchers examined a series of fissures that stretch more than a thousand kilometers (600 miles) across the lava-covered Cerberus Plains, just north of the Martian equator.
The images show geologic evidence for catastrophic floods, the scientists said in a press statement issued today. Their work is detailed in the journal Geophysical Research Letters.
The evidence centers on flat-topped, teardrop-shaped mesas that rise some 100 meters (330 feet) from the channels in which they sit. The researchers say the features are similar to structures in the Channeled Scabland in the northwestern United States.
The amount of water needed to carve the structures is estimated to be 600 cubic kilometers, four times what's in Lake Tahoe.
"What's different here is that this is very recent, and the water source is nothing like we have on Earth," said Devon Burr, a doctoral candidate in geosciences at the University of Arizona. "The water here gushed from volcano-tectonic fissures. While the fissures themselves may be older, the latest eruption of water was probably only about 10 million years ago."
The study adds to other evidence suggesting that Mars may still be geothermally active and might still have the ability to push underground water to the surface by a process called flood volcanism. Other studies have hinted that such subsurface reservoirs may exist. The heat and water provided by geothermal activity would be good news for biologists who would search for possible life on Mars.
"Flood volcanism on Earth occurs about every tens of millions of years," said Alfred McEwen, a university of Arizona planetary scientist who worked on the study. "The last such event was 10 million years ago. But that doesn't mean it's over. It will happen again. The same is probably true on Mars -- geologically speaking, it's still active."
Susan Sakimoto of the NASA Goddard Space Flight Center also worked on the study.
Other scientists have been cautious or critical of the claims over photographic evidence of water on Mars. Most researchers agree that the case won't be decided until actual water is found by a surface robot or human explorers. The possibility exists, however, that
the Mars Odyssey spacecraft, which just began its science mission at Mars this week, could detect water from its orbital position above the planet.For Martian geography buffs, the new study involved photos of the Athabasca Valles channel system that branches south and southwest from the Cerberus Fossae.
"Athabasca Valles is an almost new component in the Martian hydrological cycle," Burr said.
The fissures from which the water is thought to have emanated were likely created by tectonic forces, or a combination of tectonic and magmatic forces, the scientists say.
In the images, a broad channel floor is often lined with grooves and ridges running parallel to the streamlined mesas or to the channel walls. The grooves, about 100 meters wide (330 feet) and 10 meters deep (33 feet), are similar to Channeled Scabland grooving on Earth, the study concludes.
Other streamlined forms poking up from the channel floor are also layered but not flat-topped. These likely formed by erosion during floods over pre-existing layered terrain, Burr said.
The research team speculates that the area studied may harbor water ice near the surface, which would have been left behind during the flooding.
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