Fwd: Phobos moon samples will have bits of Mars

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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: November 12, 2013 4:51:37 PM CST
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: Phobos moon samples will have bits of Mars

11-Nov-2013
Planetary and Space Science

Mission to Mars moon could be a sample-return twofer, study suggests
Brown researchers have helped to confirm the idea that the surface of Phobos contains tons of dust, soil, and rock blown off the Martian surface by large projectile impacts. That means a sample-return mission planned by the Russian space agency could sample two celestial bodies for the price of one.
NASA

Contact: Kevin Stacey
kevin_stacey@brown.edu
401-863-3766
Brown University

 

Martian moon samples will have bits of Mars

November 11, 2013  |  Media Contact: Kevin Stacey |  401-863-3766

 

 

A mysterious little rock in its own right The Martian moon Phobos has accumulated dust and debris from the surface of Mars, knocked into its orbital path by projectiles colliding with the planet. A sample-return mission to Phobos would thus return material both from Phobos and from Mars. Credit: NASA

 

A Russian mission to the Martian moon Phobos, launching in 2020, would return samples from Phobos that contain bits and pieces of Mars itself. A new study calculates how much Martian material is on the surface of Phobos and how deep it is likely to go.

 

PROVIDENCE, R.I. [Brown University] — A planned mission to return a sample from the Martian moon Phobos will likely be a twofer, according to a study by Brown University geologists.

The study helps to 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. 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," said James Head, professor of geological sciences and an author on the study. "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 other equipment."

The research appears in the latest issue of Space and Planetary Science.

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.

This new research 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, Ramsley and Head 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 said. "So we can crunch those numbers and find out what proportion of material on the surface of Phobos comes from Mars."

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, the researchers showed.

"Only recently — in the last several 100 million years or so — has Phobos orbited so close to Mars," Ramsley said. "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 said. "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.

 

© 2013 Brown University

 

 

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Russia's Second Shot at Phobos May Return Bits of Mars As Well

by Jason Major on November 11, 2013

 

The streaked and stained surface of Phobos. Russia's second sample-return attempt may end up sending back bits of both Phobos AND Mars. (Image: NASA/MRO/HiRISE)

After the tragic failure of the first Phobos-Grunt mission to even make it out of low-Earth orbit, the Russian space agency (Roscosmos) is hoping to give it another go at Mars' largest moon with the Phobos-Grunt 2 mission in 2020. This new-and-improved version of the spacecraft will also feature a lander and return stage, and, if successful, may not only end up sending back pieces of Phobos but of Mars as well.

The origins of Phobos have long been a topic of planetary science debate. Did it form with Mars as a planet? Is it a wayward asteroid that ventured too closely to Mars? Or is it a chunk of the Red Planet blasted up into orbit from an ancient impact event? Only in-depth examination of its surface material will allow scientists to determine which scenario is most likely (or if the correct answer is really "none of the above") and Russia's ambitious Phobos-Grunt mission attempted to become the first ever to not only land on the 16-mile-wide moon but also send samples back to Earth.

Unfortunately it wasn't in the cards. After launching on Nov. 9, 2011, Phobos-Grunt's upper stage failed to ignite, stranding it in low-Earth orbit. After all attempts to re-establish communication and control of the ill-fated spacecraft failed, Phobos-Grunt crashed back to Earth on Jan. 15, impacting in the southern Pacific off the coast of Chile.

But with a decade of development already invested in the mission, Roscosmos is willing to try again. "Ad astra per aspera," as it's said, and Phobos-Grunt 2 will attempt to do in 2020 what its predecessor couldn't.

Read more: Russia to Try Again for Phobos-Grunt?

And, according to participating researchers James Head and Kenneth Ramsley from Brown University in Providence, Rhode Island, the sample mission could end up being a "twofer."

Phobos floats in front of Mars' horizon in a Mars Express image from January 2007 (ESA)

Orbiting at an altitude of only 5,840 miles (9,400 km) Phobos has been passing through plumes material periodically blown off of Mars by impact events. Its surface soil very likely contains a good amount of Mars itself, scooped up over the millennia.

"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," said Ramsley, a visiting researcher in Brown's planetary geosciences group. "So we can crunch those numbers and find out what proportion of material on the surface of Phobos comes from Mars."

Determining that ratio would then help figure out where Phobos was in Mars orbit millions of years ago, which in turn could point at its origins.

"Only recently — in the last several 100 million years or so — has Phobos orbited so close to Mars,"  Ramsley said. "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."

In addition, having an actual sample of Phobos (along with stowaway bits of Mars) in hand on Earth, as well as all the data acquired during the mission itself, would give scientists invaluable insight to the moon's as-yet-unknown internal composition.

"Phobos has really low density," said Head, professor of geological sciences at Brown and an author on the study. "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."

The study was published in Volume 87 of Space and Planetary Science (Mars impact ejecta in the regolith of Phobos: Bulk concentration and distribution.)

Source: Brown University news release and RussianSpaceWeb.com.

See more images of Phobos here.

 

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