[meteorite-list] Mystery Spheres on Mars Finally Identified

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:51 2004
Message-ID: <200403181641.IAA13913_at_zagami.jpl.nasa.gov>

http://space.com/missionlaunches/mars_blueberries_040317.html

Mystery Spheres on Mars Finally Identified
By Leonard David
space.com
17 March 2004

Scientists have learned the composition of the mysterious sphere-shaped
objects scattered across the crater floor at Meridiani Planum, the landing
site of the Opportunity Mars rover.

By using a Mössbauer Spectrometer mounted on Opportunity's robot arm, a
patch of the tiny spherules -- also called "blueberries," although they
aren't blue -- received close examination and have now been identified as
hematite.

The spectrometer is designed to study minerals that contain iron, which are
common on the Martian surface. Also used to pin down the makeup of the
spherules was the rover's Mini-Thermal Emission Spectrometer, a science
instrument that can recognize minerals formed in water.

Meridiani: shallow lake?

This new evidence further supports the hypothesis that the hematite mineral
was likely formed in a past standing body of water. The Meridiani area, it
is thought, was once a shallow lake.

Once Opportunity wheels itself out of its current shallow crater site,
scientists expect the hematite-rich spherules to litter the landscape at
Meridiani Planum.

Philip Christensen, a Mars Exploration Rover scientist from Arizona State
University in Tempe, announced the finding yesterday at the 35th annual
Lunar and Planetary Science Conference being held in Houston, Texas.

Formation via precipitation

"This finding further supports the hypothesis that these interesting 'Mars
balls' are actually sedimentary concretions, rather than any of the other
working hypotheses," said James Garvin, Lead Scientist for Mars Exploration
and the Moon at NASA Headquarters in Washington, D.C.

There have been a variety of contending theories for what may have caused
the unusual mineralogy at Meridiani, including volcanic causes.

Garvin told SPACE.com that this latest finding strongly supports the view
that the rocks in the outcrop at Meridiani have been modified by water -- a
determination made already through other research at the site.

"Hematite as a major compositional phase in the spherules supports their
formation via precipitation, rather than as impact-related fallout," Garvin
said.

"So, the story is getting better... and multiple lines of independent
evidence support water-related chemical 'processing' of the rocks," Garvin
added. "Now all we have to do is figure out what made the rocks in the first
place and how long the water may have been involved in the 'soakings'. What
a fun time!"
Received on Thu 18 Mar 2004 11:41:22 AM PST