Fwd: Study pinpoints source of Mars meteorites

Sent from my iPad

Begin forwarded message:

From: "Gary Johnson" <gjohnson144@comcast.net>
Date: March 7, 2014 9:47:01 AM CST
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: Study pinpoints source of Mars meteorites

 

Study pinpoints source of Mars meteorites

By Irene Klotz 

CAPE CANAVERAL, Florida (Reuters) - About 5 million years ago, an asteroid or comet slammed into Mars so hard that rocks and other debris launched into space.

After traveling millions of years, some eventually landed on Earth, becoming the biggest of three main types of meteorites hailing from the Red Planet.

Now researchers say they have pinpointed the source of those Martian meteorites classified as the "shergottites." The finding, if confirmed, would give scientists fresh insights into Mars' history and evolution.

"If one were able to say, 'Oh, this Martian meteorite is from exactly this spot on Mars,' then that would have significant added value to what you could get out of it," said Carl Agee, meteorite curator and director of University of New Mexico's Institute of Meteoritics.

"We'd know exactly what material it is made of, we'd know how old it was when it formed. You'd get more of the missing pieces of the puzzle of how Mars formed," Agee said.

University of Oslo planetary scientist Stephanie Werner and colleagues say they have done just that.

The shergottites, Werner said, come from a 34-mile (55-km) wide impact basin known as Mojave Crater in the planet's equatorial region.

The scientists point to the crater's large size, relative youth and chemical composition as good matches for the shergottites, which account for about 75 percent of the roughly 150 Mars meteorites found so far.

Others say the evidence is far from ironclad.

"The (study) strikes me as somewhat speculative," said Agee, who was not involved in the research.

Werner, for example, says the shergottites crystallized some 4.3 billion years ago, roughly the same age as the crater's original terrain.

But Agee said most scientists believe the shergottites are much younger.

"I'm not convinced," Agee said.

Werner's research is published in this week's issue of the journal Science.

(Editing by Kevin Gray and David Gregorio)

 

Copyright © 2014 Reuters Limited. All rights reserved. 

 

===============================================================

 

 

Big Mars Impact Gave Earth Most of Its Martian Meteorites

By Elizabeth Howell, Space.com Contributor   |   March 06, 2014 02:02pm ET

 

A look at Mojave Crater on Mars. The rays are evidence of debris thrown up from an impact that happened about five million years ago. The arrow points towards crater clusters used to estimate the age of the region. Credit: Science/AAAS View full size image

A huge meteorite impact on Mars five million years ago blasted toward Earth many of the rocks that scientists scrutinize to learn more about the Red Planet, a new study reveals.

The cosmic crash left a 34-mile-wide (55 kilometers) gouge on Mars called Mojave Crater and is the source of all "shergottite" or igneous rock Martian meteorites found on Earth, researchers say. Examining the crater and the meteorites also led to new revelations about how old the rocks are.

"We tried to find good arguments to convince ourselves that [Mojave Crater] was five million years or younger. You don't expect this size of crater so recently formed, statistically at least," lead author Stephanie Werner, a planetary scientist at the University of Oslo in Norway, told Space.com. [Mars Meteorites: Red Planet Pieces on Earth (Photos)]

Werner's team first used a technique called crater counting, which estimates a region's age by seeing how many large and small craters are in a particular zone. The more large craters, the older the terrain likely is.

 

Through their detective work, Werner said, they found the crater is indeed about five million years old. The material blasted from Mojave Crater had fewer meteorite strikes than the surrounding channel floor.

 

Mojave Crater's interior in a picture taken by NASA's Mars Reconnaissance Orbiter.
Credit: Science/AAAS

View full size image

 

 

 

Age dispute

Mineral studies of Mojave Crater using NASA's Mars Reconnaissance Orbiter and the European Space Agency's Mars Express orbiter revealed a good match with shergottites, as both the meteorites and the crater had pyroxene minerals in similar abundances.

The find, however, yielded an age mystery. Shergottites (which make up about 75 percent of Mars meteorites found on Earth) appear to be youngsters despite their origins. While a plateau around Mojave Crater is 4.3 billion years old, shergottites were believed to have crystallized (or solidified) between about 150 million years ago and 600 million years ago. Reconciling the difference was Werner's team's next step.

The study suggests scientists underestimated the shergottites' crystallization age because the rocks were "reset" by melting events. Meteorite impacts, tectonic activity and volcanic eruptions could do this, researchers said. Once the rock is broken up with heat or geochemical processes, when it is reformed it would appear much younger than it actually is.

So the shergottites are probably around 4.3 billion years old, Werner said, adding that this conclusion is the most "provocative" part of the study.

"It will be quite interesting to see how that will be discussed in the future," she said.

 

Copyright © 2014 TechMediaNetwork.com All rights reserved.

 

===============================================================