Once thought dead, Mars spewed floods of lava big enough to bury Canada in recent geologic time, with many eruptions during the past 10 million to 100 million years and others perhaps within the last 3 million years Once thought dead,
Mars spewed floods of lava big enough to bury Canada in recent geologic time, with many eruptions occurring during the past 10 million to 100 million years, and others perhaps within the last 3 million years."Volcanism is therefore likely to be an active geological process in current geological time in a few localized areas on Mars," concluded a new study by William K. Hartmann and Daniel C. Berman of the Planetary Science Institute in Tucson, Arizona.
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They analyzed photographs taken by NASAs
Mars Global Surveyor spacecraft, counting craters to estimate the dates of lava flows on the vast Elysium Plains that straddle the Martian equator. Younger flows generally have fewer craters than older ones. "When I look for the youngest flows, I come up with 10 million to 100 million years, and possibly down to a few million years," Hartmann said. "These are the youngest flows found so far on Mars."
He said the youngest flows are part of a Canada-sized area of relatively young, overlapping flows that spewed from fissures onto the southern
Elysium Plains and part of the nearby Amazonis plains.
This older lava flow on Mars' Elysium Plains is more eroded and heavily cratered than geologically recent flows.
The young flows show Mars "has much more recent volcanism and subsurface heating than anyone expected," Hartmann said. "If there has been volcanism throughout [4.6 billion years of] Martian history up until a few million years ago, its unlikely it stopped just before we got there. So its probable volcanic eruptions will continue in the future."
Ongoing volcanic heating likely melted subsurface ice to create ground water that gushed onto Martian slopes in very recent times -- a discovery reported by other scientists last month, he said.
"The big story is relatively recent activity of all sorts on Mars, not only volcanism, but also fluid water," Hartmann said. "If you are heating some areas hot enough to melt rock and produce lava eruptions in the last 10 million or 100 million years, then you must heat lots and lots of areas enough to melt ice in the ground. You are not going to produce young volcanism without producing young surface or subsurface water flow."
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Recent volcanism "means that if we are looking for life, there are heat sources and liquid water under the ground -- possibly even today," he added. "Those could be great habitats for microbes. They are Yellowstone Parks on Mars."
Young lava flows also suggest where "astronauts on Mars might be able to tap into geothermal energy sources for long-term habitation sites," Hartmann said.
Hartmann and Berman, planetary scientists, published their findings last month in the Journal of Geophysical Research Planets. An accompanying study described the giant lava flows.
A young, sparsely cratered Martian lava flow (bottom half) laps against the upper rim crest of an older 3-mile- (5-kilometer-) wide impact crater.
"Flood volcanism is one of the most significant crust-forming processes identified on Mars," said the authors of that study, including Alfred McEwen of the University of Arizona. "The extreme paucity of craters in some of the images of the flood lavas suggests that this style of volcanism might plausibly persist to this day on Mars."
If Global Surveyor spotted flows only several million years old, "there is no way we just happened to see the very last gasp," McEwen said. "There will be future volcanism. But dont hold your breath. It may take a few million years."
Hartmann said eruptions might be thousands to millions of years apart, so Global Surveyor is unlikely to see any, just as "you could fly over North America for a long time and not see new lava flows. But if you wait long enough, there will be another eruption."
McEwen said Hartmann and Berman dated one Martian lava flow at 1 million years old, "but they prefer to say 10 million to be safe."
Since the new study was submitted, Hartmann said more research suggests the youngest flows are closer to 10 million years old.
"Lava flows in the last few million years are still a possibility," said Frank Palluconi, deputy project scientist for Mars Global Surveyor at NASAs
Jet Propulsion Laboratory in Pasadena, California.He said that conclusion is based both on cratering studies such as Hartmanns and the lack of sand dune fields atop young lava flows.
"Hartmanns results are really quite convincing," said planetary geologist Mike Carr of the U.S. Geological Survey in Menlo Park, California.
Carr was not surprised by evidence of volcanism within the past several million years because some meteorites that were hurled off Mars and onto Earth by asteroid impacts are made of volcanic rock formed 150 million years ago, which "is yesterday geologically."
"Mars is surely volcanically active today," Carr said. "That doesnt mean were going to see volcanoes like we do on [Jupiters moon] Io. Maybe every 10,000 years there is an eruption, or something like that."
Hartmann said Mars once was thought dead volcanically because it is smaller than Earth and should have cooled much sooner -- perhaps 2 billion years ago.
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