A pair of long gashes in the surface of Mars associated with a towering volcano shows evidence of marsquakes that could have occurred within the past few million years, and perhaps within modern times, according to new research.
If such activity is recent, and it can be traced to the volcano, it would imply that the mountain is still active – its magma providing a source of heat to melt ice and provide potential habitats for simple forms of life.
The gash is one of a pair of parallel features known collectively as Cerberus Fossae. These appear to be enormous collapsed lava dikes formed during eruptions of Elysium Mons, a volcano that vaults more than eight miles above the vast lava fields that surround it.
The mountain is thought to have been active within the past 2 million years. In principle, it still could be, with magma working its way down the flanks through subsurface conduits, rather than through repeated surface eruptions.
In 2010, another team of researchers hunting for heat sources on the Martian surface with an instrument aboard NASA's Mars Odyssey orbiter reported that they had detected warmth in the gashes, known as graben. The team noted that the signatures were hard to explain without invoking a subterranean source of heat.
Now, a team of researchers interested in faults on Mars says patterns of fallen boulders in both graben testify to marsquakes.
The team estimates that the temblors have occurred over a geologically recent span of time that could include the present day. If the evidence they see resulted from one quake, it would have registered at least a magnitude 7.5 had it occurred on Earth, comparable to an earthquake that devastated eastern Turkey last year. The results appear tomorrow in the Journal of Geophysical Research – Planets.
The link between volcanoes, active faults, and potential habitats "makes the boulder data we have collected so intriguing," said Gerald Roberts, a geophysicist at the University of London who led the British-Italian team that conducted the study, in a prepared statement.
Using boulders as benchmarks for earthquake activity is one way to get around the dearth of instruments on Mars for taking the geophysical pulse of the planet. So far, NASA's Viking landers, which arrived at Mars in the mid 1970s, are the only platforms that carried seismometers to Mars, notes James Head III, a planetary scientist at Brown University in Providence, R.I., who studies volcanoes, quakes, and tectonics on other planets.
Unfortunately, he adds, the only shaking they detected came from vibrations as wind buffeted the landers.
Indeed, he adds, "it's pretty remarkably abysmal" that basic information gleaned from seismometers – from the structure of a planet's interior to the level of quake activity – is still lacking for Mars. Scientists have had to turn to Earth's moon as a model for what the structure of Mars' crust might be like. Apollo astronauts left seismometers on the moon that operated until 1977 and revealed a great deal about the moon's structure.
Given the paucity of data on quake activity on Mars, Dr. Gordon's team has provided a "great analysis and is very thought-provoking," says Dr. Head, who was not part of the team.