Possibility of Past Water on Mars Takes a Hit


Images of Mars taken from orbit show a massive system of riverbeds and canyons etched by water. Or maybe not. A new study of one channel shows that it was formed by lava flow and not water, and the results make “a strong case that fluid lava can produce channels that look very much like water-generated features,” said Jim Zimbelman from the Smithsonian Institution in Washington, one of the researchers. “So, we should not jump to a water-related conclusion when we see such channels on other planets.”

Whether channels on Mars were formed by water or by lava has been debated for years and the outcome is thought to influence the likelihood of finding life there. Images from various Mars orbiters reveal details resembling the erosion of soil by water: terracing of channel walls, formation of small islands in a channel, hanging channels that dead-end and braided channels that branch off and then reconnect to the main branch. “These are thought to be clear evidence of fluvial [water-based] erosion on Mars,” said Jacob Bleacher from Goddard Spaceflight Center, who presented the results at the Lunar and Planetary Science Conference last week.

Lava flow usually creates big, open channels, such as the ones commonly seen in Hawaii. But detailed looks at both channels on Mars and in Hawaii shed a whole new light on the formation of channels and other features on Mars.

The research team carried out a careful study of a single channel on the southwest flank of Mars’ Ascraeus Mons volcano, one of the three clustered volcanoes collectively called the Tharsis Montes. To piece together images covering more than 270 kilometers (~168 miles) of this channel, the team relied on high-resolution pictures from three cameras—the Thermal Emission Imaging System (THEMIS), the Context Imager (CTX) and the High/Super Resolution Stereo Color (HRSC) imager—as well as earlier data from the Mars Orbiter Laser Altimeter (MOLA). These data gave a much more detailed view of the surface than previously available.

Because the fluid that formed this and other Ascraeus Mons channels is long-gone, its identity has been hard to deduce, but the visual clues at the source of the channel seem to point to water. These clues include small islands, secondary channels that branch off and rejoin the main one and eroded bars on the insides of the curves of the channels.

The Tharsis region of Mars, including the three volcanoes of Tharsis Montes (Arsia, Pavonis and Ascraeus Mons), as well as Olympic Mons in the upper left corner. Credit: NASA/Jet Propulsion Lab

But at the channel’s other end, an area not clearly seen before, the team found a ridge that appears to have lava flows coming out of it. In some areas, “the channel is actually roofed over, as if it were a lava tube, and lined up along this, we see several rootless vents,” or openings where lava is forced out of the tube and creates small structures, he explains. These types of features don’t form in water-carved channels, he notes. Bleacher argues that having one end of the channel formed by water and the other end by lava is an “exotic” combination. More likely, he thinks, the entire channel was formed by lava.

To find out what kinds of features lava can produce, Bleacher, Zimbelman and W. Brent Garry examined the 51-kilometer (~32 mile) lava flow from the 1859 eruption of Mauna Loa on the Big Island of Hawaii. Their main focus was an island nearly a kilometer long in the middle of the channel; Bleacher says this is much larger than islands typically identified within lava flows. To survey the island, the team used differential GPS, which provides location information to within about 3 to 5 centimeters (1.1 to 1.9 inches), rather than the roughly 3 to 5 meters (9.8 to 16.4 feet) that a car’s GPS can offer.

“We found terraced walls on the insides of these channels, channels that go out and just disappear, channels that cut back into the main one, and vertical walls 9 meters (~29 feet) high,” Bleacher says. “So, right here, in something that we know was formed only by flowing lava, we found most of the features that were considered to be diagnostic of water-carved channels on Mars.”

Further evidence that such features could be created by lava flows came from the examination of a detailed image of channels from the Mare Imbrium, a dark patch on the moon that is actually a large crater filled with ancient lava rock. In this image, too, the researchers found channels with terraced walls and branching secondary channels.

The conclusion that lava probably made the channel on Mars “not only has implications for the geological evolution of the Ascraeus Mons but also the whole Tharsis Bulge [volcanic region],” says Andy de Wet, a co-author at Franklin & Marshall College, Lancaster, Penn. “It may also have some implications for the supposed widespread involvement of water in the geological evolution of Mars.”

Source: NASA

6 Replies to “Possibility of Past Water on Mars Takes a Hit”

  1. I think the Mars community as a while has been very cautious when labeling things as water based.

    Mars has a very complex geology, which involves water, volcanism, wind… We measure the quantities of water on the planet today, we see the water and CO2 seasonal cycles, there are basins with sedimentary rock layers in basins, etc… But obviously not every land feature is a result of water flow.

    Otherwise, how can a guy called “Andy de Wet” argue that something was NOT formed by water?!

  2. I wonder how they compared the surface geological properties in Hawaii to that of Mars since we haven’t ever brought rocks back from Mars? And what about the reduced gravity of Mars when compared to Earth? Surely water or lava flows would behave differently from planet to planet…

    Interesting study none the less.

  3. I would agree that its hard to know from here if its a water, volcanism or wind feature on Mars (or other) and we can all cite examples and argue until we are blue in the face.

    That is why we need sample return missions, and more importantly us geologists need to get there.

  4. Its possible at one point there was water, but we know there was volcanic activity for sure, it all depends if Mars ever had a fairly thick stable atmoshere, we need to prove that first.

  5. I’ve always been suspicious of liquid water on Mars. The Sun has never been warmer and, to my knowledge, Mars has never been closer to the Sun. And it’s COLD on Mars! Very cold! Way too cold for water to persist as a liquid for any length of time. How or why this small detail is overlooked has puzzled me for years. It looks like water erosion, but if that’s not possible then there’s gotta be another explanaion.

  6. I have no doubt that there are cannels on Mars that were formed by lave. Mars has enough volcanos. I also am pretty darn sure that some channels were created by liquid running water. (The sun was warmer in it’s past and it is a variable star, not very variable maybe, but it is variable. Remember, neoguru, that the Earth was also a lot warmer than it is today. It has also been a lot colder than it is today.) I say some channels are lava generated and some are water generated. It is only common sense.

Comments are closed.