The image shows the orbits of the Martian moons Phobos and Deimos and the spread of potential particle trajectories from an asteroid impact on Mars. (Purdue University image/courtesy of Loic Chappaz)
Phobos – one of two moons of Mars – could well be the site for life detection beyond Earth.
That’s the belief of Purdue University researchers, arguing that Phobos may be an extraterrestrial repository for microbes blasted off of Mars by being on the receiving end of asteroid hits.
“A sample from the moon Phobos, which is much easier to reach than the Red Planet itself, would almost surely contain Martian material blasted off from large asteroid impacts. If life on Mars exists or existed within the last 10 million years, a mission to Phobos could yield our first evidence of life beyond Earth,” said Jay Melosh, a distinguished professor of earth, atmospheric and planetary sciences and physics and aerospace engineering at Purdue in West Lafayette, Indiana.
Melosh and fellow researchers combined their expertise in impact cratering and orbital mechanics. By melding their talents, they appraised how much material was displaced by particular asteroid impacts and whether individual particles would land on Phobos, the closer of the two Martian moons.
Pathways of particles
The team concluded that a 200-gram sample scooped from the surface of Phobos could contain, on average, about one-tenth of a milligram of Mars surface material launched in the past 10 million years and 50 billion individual particles from Mars.
The same sample could contain as much as 50 milligrams of Mars surface material from the past 3.5 billion years.
The team followed the possible paths the tiny particles could take as they were hurtled from the planet’s surface through space, examining possible speeds, angles of departure and orbital forces. The team plotted more than 10 million trajectories and evaluated which would intercept Phobos and where they might land on the moon during its eight-hour orbit around Mars.
“It is estimated that during the past 10 million years there have been at least four large impact events powerful enough to launch material into space, and we focused on several large craters as possible points of origin,” said graduate students, Loic Chappaz.
“It turns out that no matter where Phobos is in its orbit, it would have captured material from these powerful impact events,” Chappaz said.
Rich with information
It is thought that after 10 million years of exposure to the high levels of radiation on Phobos, any biologically active material would be destroyed, said Kathleen Howell, the Hsu Lo Professor of Aeronautical and Astronautical Engineering. “Of course older Martian material would still be rich with information, but there would be much less concern about bringing a viable organism back to Earth and necessary quarantine measures.”
According to Melosh: “It is not outside the realm of possibility that a sample could contain a dormant organism that might wake up when exposed to more favorable conditions on Earth.”
But that brings up the specter of Andromeda Strain – a virulent microbe from space that doesn’t play nice with Earth’s biosphere.
However, a fatal contamination is unlikely, Melosh said.
“Approximately one ton of Martian material lands on Earth every year,” Melosh noted. “There is a lot more swapping back and forth of material within our solar system than people realize. In fact, we may owe our existence to life on Mars,” he said in a university press statement.
By Leonard David