Are We All From Mars?
A T L A N T A, Jan. 12 -- New calculations show through the history of the solar system, billions of Martian rocks blasted into space by colliding comets and meteors eventually crashed into Earth, and vice versa.
Experiments also show microbes thathitched along could have survived interplanetary flight.
What’s left unanswered is whether there were any Martian microbes to maketheir way to Earth.
But also unanswered is the intriguing possibility that maybe we’re all fromMars, or at least descendents of Martians.
“We don’t know where life first started,” says Curt Mileikowsky, a physicistwith the Royal Institute of Technology in Sweden, “but we know Mars wasavailable for life earlier than Earth.”
Mars, smaller than Earth, would have cooled to hospitable temperaturesfirst. And most planetary scientists envision that early Mars would havebeen a warm, wet place — conditions considered amenable to life.
In the work, Mileikowsky and nine other researchers from institutions aroundthe world calculated that meteors and comets crashing into the Red Planetwould have knocked billions of Martian rocks into space, some as large asboulders. About one of every 150 of those Martian rocks then fell on Earthwithin a million years, the researchers said.
In total, more than 5 billion Martian rocks have fallen to Earth in the past4 billion years. Before that, in the first half billion years of the solarsystem’s history, when there was a lot more stuff whizzing through, some 50 billion Martian rocks would have tumbled down on Earth.
The findings were presented today at the American Astronomical Societymeeting in Atlanta. A scientific paper describing the calculations has alsobeen submitted to the journal Icarus.
Earth to Mars As WellThe rocky interplanetary highway isn’t just one way. Comets and meteors alsoblasted pieces of Earth into space, some of which made their way to Mars, though notquite as many. (The reasons: Earth’s gravity is stronger, so not as manyrocks make it into outer space. Mars is farther out, so the rocks need anextra kick to get out to Mars orbit. And the smaller Mars is a smallertarget to hit.)
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