Mars
appears to be a calm and desolate planet, but scientists now think something
big is brewing beneath its wind-swept surface.
New
research on Hawaiian volcanoes, combined with satellite imagery
of Mars, suggests that three Martian volcanoes may only be dormant—not
extinct. Instead of Mars' crust moving over stationary magma "hot
spots," as occurs on Earth, researchers think the plumes travel.
"On
Earth, the Hawaiian islands were built from volcanoes that erupted as the Earth's
crust slid over a hot spot—a plume of rising magma," said Jacob Bleacher,
a planetary scientist at Arizona State University and NASA's Goddard Space
Flight Center in Greenbelt, Md. "Our research raises the possibility that
the opposite happens on Mars; a plume might move beneath stationary
crust."
Bleacher and
his colleagues' findings are detailed in a recent issue of the Journal of
Geophysical Research, Planets.
Sleeping
giants?
Each of the
volcanoes, located in the Tharsis region of Mars, is about 186 miles (300
kilometers) across. The largest volcano on Earth, Mauna Loa, is only 60 miles
(97 kilometers) across.
Although scientists
have never observed a volcanic Mars, recent
images from the European Space Agency's Mars Express missions suggest the
volcanoes there have been active within the past two million years and might
still be. Also, the sparse impact craters near the three Tharsis volcanoes indicate
relatively recent eruptions.
Lava flows
show that these recent eruptions oozed from large cracks on the volcanoes'
sides, occurring in a chain that meandered northeast.
"We
thought we could take what we learned about lava flow features on Hawaiian
volcanoes and apply it to Martian
volcanoes to reveal their history," Bleacher said. But until recently,
images of Mars weren't detailed enough to make a good comparison, he noted.
Traveling
hot spot
Armed with
new images from NASA's Mars Odyssey and Mars Global Surveyor orbiters, as well
as the ESA's Mars Express, the team saw that the three volcanoes were similar
in formation. However, each had recently erupted in distinct ways that allowed the
scientists to determine the ages of the eruptions.
During the volcanic
activity, lava oozed from cracks in the volcanoes' sides and formed "lava
aprons;" the smoother the apron, scientists determined, the older the
eruption.
Lava aprons
on the northern-most volcano, Ascraeus Mons, are the youngest, Bleacher said, while
the southern-most volcano, Arsia Mons, has the oldest. Like the Hawaiian
volcanoes, the findings show that the volcanoes were fed by a common source
of magma—but one that was on the move.
There's an
alternative explanation for the chain of activity. Scientists postulate that
the plume of magma could have spread out once it impacted the crust from below,
like smoke hitting a ceiling.
"Our
evidence doesn't favor either scenario," Bleacher said, "but one way
to explain the trends we see is for a plume to move under the stationary
Martian crust." If true, the traveling plume of magma could pass beneath
dormant Martian volcanoes and stir them from sleep.
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