msnbc.com (Boyle/Oberg): NASA frees rover from Martian sand trap

After inch-by-inch progress, Opportunity back on track

http://www.msnbc.msn.com/id/8098155

By Alan Boyle, Science editor, MSNBC

NBC News space analyst James Oberg contributed to this report.

Updated: 2:03 p.m. ET June 4, 2005

NASA's Opportunity rover has broken free from the Martian sand dune where it had been stuck for more than a month, the mission's top scientist announced Saturday.

"We're out!" Cornell astronomer Steve Squyres, principal investigator for the Mars Exploration Rovers, reported in a mission update.

Squyres said data from the previous day's activities at Meridiani Planum indicated that "all six wheels are on top of the soil."

"We've been confident all along that this would happen, but still... what a relief!" he wrote.

The Opportunity rover and Spirit, its twin on the other side of Mars, have been studying the Red Planet from the surface since January 2004, and last year Opportunity sent back headline-grabbing evidence that its landing site was drenched with water in ancient times.

In late April, during a southward trek toward a crater of interest called Erebus, Opportunity's wheels became mired in the crest of a sand dune — and mission managers took weeks to plot out a strategy for getting out of the dune.

The rover team commanded the machine to reposition its wheels, then go through a series of spins that pushed the rover forward an inch at a time.

Opportunity broke free after making about 3 feet (93 centimeters) of that inch-by-inch progress.

JimO adds: now thay can resume the thinking along these lines (from Squyres' on-line journal)

April 18, 2005 -- We're starting to plan our attack on Erebus crater. It's complicated a little bit by the fact that Erebus is actually nested inside an even larger crater that we've named Terra Nova. Terra Nova is very old and subdued in its topography, so it probably doesn't expose a lot of stratigraphy. The current plan is that we'll hit Erebus somewhere along its northern rim, take a big panorama, and then decide what to do in detail... similar to what we did when we first arrived at Endurance crater. It'd be nice to plan it in detail now, but we simply need to learn more before we can do that.

April 17, 2005 -- The big science news for Opportunity is that we are now in the etched terrain. This crept up on us slowly, but we're now starting to understand what etched terrain looks like. We've known for a long time that the etched terrain has a "grain" to it, visible in orbital images, that runs north-south. And what we now realize is that the grain is caused by the very large ripples that we've been driving through. These ripples look different from the ones that we saw farther north. The obvious difference is that they're a lot bigger, but that't not all. Look at some of the recent pictures and you'll see what I'm talking about. We're going to look them over pretty carefully as we continue to the south. And speaking of continuing south, we're now only half a kilometer or so away from Erebus crater, the next major landmark. This thing is big, at least in terms of diameter... it's about twice the diameter of Endurance crater. It doesn't appear to be nearly as deep, but we're still hoping that it'll have some significant topography. We'll see when we get there.