"This work shows that samples from Mars can indeed be found in the soil of Phobos, and how their concentration might change with depth. That will be critical in the design of the drills and other equipment," says James Head. (Credit: JihemD/Wikimedia Commons)

Sample from Mars moon mission could be a twofer

A planned Russian mission in 2020 to return a sample from the Martian moon Phobos will likely not only contain bits and pieces of the moon—but also of Mars itself.

A new study helps confirm the idea that the surface of Phobos contains tons of dust, soil, and rock blown off the Martian surface by large projectile impacts. Phobos’ orbital path plows through occasional plumes of Martian debris, meaning the tiny moon has been gathering Martian castoffs for millions of years.

The Stickney Crater on Phobos. The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter took two images of the larger of Mars' two moons, Phobos, within 10 minutes of each other on 23 March 2008. This is the first, taken from a distance of about 6,800 kilometers (about 4,200 miles). It is presented in color by combining data from the camera's blue-green, red, and near-infrared channels. (Credit: NASA/JPL-Caltech/University of Arizona)
The Stickney Crater on Phobos. The High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter took two images of the larger of Mars’ two moons, Phobos, within 10 minutes of each other on 23 March 2008. This is the first, taken from a distance of about 6,800 kilometers (about 4,200 miles). It is presented in color by combining data from the camera’s blue-green, red, and near-infrared channels. (Credit: NASA/JPL-Caltech/University of Arizona)

That means a sample-return mission planned by the Russian space agency could sample two celestial bodies for the price of one.

“The mission is scheduled to be flown early in the next decade, so the question is not academic,” says James Head, professor of geological sciences at Brown University. “This work shows that samples from Mars can indeed be found in the soil of Phobos, and how their concentration might change with depth. That will be critical in the design of the drills and other equipment.”

Failed first attempt

The Russian mission will be the space agency’s second attempt to return a sample from Phobos. Head was a participating scientist on the first try, which launched in 2011, but an engine failure felled the spacecraft before it could leave Earth orbit. The next attempt is scheduled to launch in 2020 or shortly thereafter.

The new research, published in Space and Planetary Science, grew out of preparation for the original mission, which would still be en route to Phobos had it not encountered problems.

Scientists had long assumed Phobos likely contained Martian bits, but Russian mission planners wanted to know just how much might be there and where it might be found. They turned to Head and Ken Ramsley, a visiting researcher in Brown’s planetary geosciences group.

To answer those questions, the scientists started with a model based on our own Moon to estimate how much of Phobos’ regolith (loose rock and dust on the surface) would come from projectiles. They then used gravitational and orbital data to determine what proportion of that projectile material came from Mars.

“When an impactor hits Mars, only a certain of proportion of ejecta will have enough velocity to reach the altitude of Phobos, and Phobos’ orbital path intersects only a certain proportion of that,” Ramsley says. “So we can crunch those numbers and find out what proportion of material on the surface of Phobos comes from Mars.”

Mars mission bonus

According to those calculations, the regolith on Phobos should contain Martian material at a rate of about 250 parts per million. The Martian bits should be distributed fairly evenly across the surface, mostly in the upper layers of regolith.

“Only recently—in the last several 100 million years or so—has Phobos orbited so close to Mars,” Ramsley says. “In the distant past it orbited much higher up. So that’s why you’re going to see probably 10 to 100 times higher concentration in the upper regolith as opposed to deeper down.”

And while 250 parts per million doesn’t sound like a lot, the possibility of returning even a little Martian material to Earth gets planetary scientists excited. It’s a nice bonus for a mission primarily aimed at learning more about Phobos, a mysterious little rock in its own right.

Scientists are still not sure where it came from. Is it a chunk of Mars that was knocked off by an impact early in Martian history, or is it an asteroid snared in Mars’s orbit? There are also questions about whether its interior might hold significant amounts of water.

“Phobos has really low density,” Head says. “Is that low density due to ice in its interior or is it due to Phobos being completely fragmented, like a loose rubble pile? We don’t know.”

If all goes well, the upcoming Russian mission will help solve some of those mysteries about Phobos. And we might learn a good deal about Mars in the process.

Source: Brown University

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  1. Babu G. Ranganathan

    ANY LIFE ON MARS CAME FROM EARTH

    In the Earth’s past there was powerful volcanic activity which could have easily spewed dirt and rocks containing microbes into outer space which not only could have eventually reached Mars but also ended up traveling in orbit through space that we now know as meteors. A Newsweek article of September 21, 1998, p.12 mentions exactly this possibility. “We think there’s about 7 million tons of earth soil sitting on Mars”, says scientist and evolutionist Kenneth Nealson. “You have to consider the possibility that if we find life on Mars, it could have come from the Earth” [Weingarten, T., Newsweek, September 21, 1998, p.12].

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    Proteins can’t come into existence unless there’s life first! Miller, in his famous experiment in 1953, showed that individual amino acids (the building blocks of life) could come into existence by chance. But, it’s not enough just to have amino acids. The various amino acids that make-up life must link together in a precise sequence, just like the letters in a sentence, to form functioning protein molecules. If they’re not in the right sequence the protein molecules won’t work. It has never been shown that various amino acids can bind together into a sequence by chance to form protein molecules. Even the simplest cell is made up of many millions of various protein molecules.

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    Also, what many don’t realize is that Miller had a laboratory apparatus that shielded and protected the individual amino acids the moment they were formed, otherwise the amino acids would have quickly disintegrated and been destroyed in the mix of random energy and forces involved in Miller’s experiment.

    There is no innate chemical tendency for the various amino acids to bond with one another in a sequence. Any one amino acid can just as easily bond with any other. The only reason at all for why the various amino acids bond with one another in a precise sequence in the cells of our bodies is because they’re directed to do so by an already existing sequence of molecules found in our genetic code.

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