[meteorite-list] Phoenix Mars Lander: The Search For A Safe Haven

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 10 Jan 2007 10:21:16 -0800 (PST)
Message-ID: <200701101821.KAA28772_at_zagami.jpl.nasa.gov>

http://space.com/businesstechnology/070110_mar_phoenix_landing.html

Phoenix Mars Lander: The Search For A Safe Haven
By Leonard David
space.com
10 January 2007

As NASA prepares its Mars Phoenix spacecraft for an August launch,
program officials are still trying to find a suitable landing site.

Using data from two spacecraft - Mars Odyssey and the Mars
Reconnaissance Orbiter - already orbiting the red planet, mission
managers are searching for a landing zone near the northern polar
region where there is a permanent ice cap.

Finding the right spot has not been easy. One favored area, for example,
has already been vetoed because too many large boulders with
spacecraft-eating potential were spotted there

The $386 million Phoenix lander mission will be the first to fly under
the rubric of NASA's "Scout" program. Once safely down on martian real
estate, the lander is to use a sturdy arm to dig for subsurface water
ice. The lander is outfitted with a set of instruments designed to help
scientists glean clues to climate change on Mars, anjd search for
potential habitats that might support life.

Puzzled heads

NASA's Mars Odyssey has been orbiting the red planet since October 2001.
One of its primary instruments is the Thermal Emission Imaging System -
called Themis for short. This camera operates in the visible and
infrared parts of the spectrum and has been busy determining the
distribution of minerals on the surface of Mars.

A particularly cool feature of Themis is that in the martian night it
maps heat radiating from rocks on the planet's surface. And when Themis
focused in on Region B - the top candidate for the Phoenix landing zone
- it was an eye-opener.

"Region B was just speckled with little hot spots that we now know are
rock and boulder fields," said Philip Christensen at Arizona State
University in Tempe, a leading Mars researcher and Principal
Investigator for Odyssey's Themis instrument.

"There are more big rocks than we've seen at any other landing site,"
Christensen said. "I think there were a lot of puzzled heads wondering,
wow, where did all these big rocks come from?"

Imaging campaign

In the quest to find a safe haven for Phoenix, Odyssey has been one busy
bird, Christensen said.

"Half of the Themis bits coming from the spacecraft are devoted to the
site survey for Phoenix. We are making a significant number of thermal
maps of the candidate landing site areas," Christensen said.

Christensen added that the collaboration - an imaging campaign - between
Themis' thermal data and the super-powerful Mars Reconnaissance
Orbiter's (MRO) High Resolution Science Imaging Experiment (HiRISE) has
been going extremely well.

"We are using Themis data very successfully to narrow down the choice of
sites, as HiRISE focuses on the areas where Themis data show the ground
is largely rock-free," Christensen noted.

Safety point of view

It was the zoom lens of MRO's HiRISE that aced out Region B as the
Phoenix landing locale. Numbers of big rocks became a big issue with
receipt of the first HiRISE shots late last year.

"Everything was looking good until [they received the] HiRISE images.
They just blew us away. Mars just did it to us again," said Ray
Arvidson, a Phoenix science team member from Washington University in
St. Louis, Missouri.

Why there's an abundance of rocks in that zone is a brainteaser,
Arvidson noted. Perhaps thick deposits of windblown dust are underneath
the rocks, causing them to rise up on top of this dust mantle. Or
climate changes have expanded and contracted the icy landscape, forcing
large rocks topside, he suggested.

"Either way - we just didn't expect Mars to have kept its rocks on the
surface," Arvidson said. "From a safety point of view, what counts is
the number of rocks - and a lot of the rocks were bigger than the lander."

The task now, Arvidson observed, is interpolating between the ground
truth as revealed by HiRISE and the pre-dawn Themis data.

And the nice news is that three prospective Phoenix landing areas have
been pinpointed.

Looking good

Anxious to identify a happy address on Mars for Phoenix is Peter Smith,
Phoenix Principal Investigator at the University of Arizona's Lunar and
Planetary Laboratory in Tucson.

Smith said that Odyssey's Themis nighttime infrared is delineating the
locations of the hot rocks. Meanwhile, HiRISE images quantify local rock
concentrations.

This doubling up of spacecraft has yielded a powerful combination of
information to provide both coverage and high resolution of the
"latitude girdle" between 65 and 72 north in which Phoenix is to land,
Smith said.

"After finding three potential landing sites, we are quite hopeful that
the scary, boulder-strewn surfaces first seen last October can be
avoided completely," Smith pointed out. "Data that will verify this
claim are still coming down from Mars - but our next landing site meeting
on January 22 will summarize the search and lead to the identification
of our best sites."

Alfred McEwen, principal investigator for the HiRISE instrument and
Director of the University of Arizona's Planetary Image Research Lab,
said HiRISE images acquired over the past few weeks - concentrated over
the new candidate landing ellipses - have shown far fewer boulders than
images of the previous candidates.

"So it's looking good," McEwen concluded.
Received on Wed 10 Jan 2007 01:21:16 PM PST