Mars and Venus, those seemingly contrasting planets of
self-help book fame, have more in common than you might think. Two nearly
identical spacecraft around Mars and Venus have compared the two worlds'
atmospheres and found them to be surprisingly similar.
The ESA's Mars
Express and Venus
Express are currently in orbit around the planets taking measurements of
their atmospheres as they interact with solar radiation. The data show that
charged particles from the gas layers around both planets are being scavenged
by solar wind and storms.
"Mars and Venus are very different planets," said
David Brain, a planetary scientist at the University of California, Berkeley,
and a supporting investigator for Venus Express. "Venus's atmosphere is
very thick, dry and hot, and Mars's atmosphere is very thin and cold. And yet
the same processes are happening on both planets."
Both Venus's and Mars's atmospheres are about 95 percent
carbon dioxide. Earth's is mostly nitrogen now, but scientists think it used to
be more like the other rocky worlds.
Because neither of our neighboring planets has a global,
protecive magnetic field, the solar wind is free to interact directly with the
planets' atmospheres. Solar radiation energizes atmospheric particles so that
they accelerate and escape from the planets. Earth is spared from the brunt of
solar radiation by its protective
magnetosphere.
"These results really highlight what a special place
Earth is and how lucky we are to have an atmosphere protected by a magnetic
field," Brain said.
By analyzing the spacecrafts' treasure trove of data,
researchers hope to learn how these two planets' climates have changed over
time and to compare their evolution to Earth's atmosphere.
"We want to understand why Earth is different from Mars,
why is it different from Venus, why are the inner planets different from the
outer planets," Brain told SPACE.com. "As a scientist it's
amazing to have the same set of measurements at both planets simultaneously. A
great example is the solar
storm. We got to see the same event measured at two different places."
In December 2006, a powerful solar storm erupted, spraying
jets of charged particles outward. Venus and Mars were smacked with radiation,
causing particles in their atmospheres to gain energy and escape — Mars lost
atmospheric particles 10 times faster than it usually does.
"I like to think of the solar storms as tsunamis in the
atmospheres of the planets," Brain said. "It was very intense and
saturated many of our instruments. It was a lucky encounter, maybe not for the
atmospheres, but for us who were watching."
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