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Mission Update by Steve Squyres

(Return to archived mission updates list)

April 2005
April 27, 2005

A note to all you Opportunity fans: Get used to the current scenery, because we're going to be here awhile.

We are very optimistic that we'll be able to get out of here, but we're really going to take our time doing it. The first rule in a situation like this is "do no harm", which means that you don't rush anything. We're going to take lots of pictures of all the terrain around the vehicle, to get a very complete picture of the situation. We're going to do lots of testing with the rovers that we have on the ground to simulate the situation on Mars. This testing will be aimed not just at finding a plan that will work, but at finding the very best plan that will work. We may try quite a few small maneuvers with Opportunity that aren't intended to do anything other then help us gather more information... perhaps followed by even more testing. All of this is going to take a lot of time. But this is a very precious vehicle up there, in excellent health, and there's no reason to rush anything. I'll try to provide updates as the process moves forward, but the main message for now is to be very, very patient. No apparent progress in the images doesn't mean anything other than that we're being very careful to do our jobs right.

April 26, 2005

Interesting stuff happening on both sides of the planet. Spirit has downlinked some spectacular Pancam images of Methuselah, showing that it is a very finely layered rock. This is indeed the best piece of layered bedrock Spirit has ever seen. Check out some of the Pancam images from Sols 464 and 465. We've picked a target on the outcrop that we've named Keystone, and we soon should be in position to do some serious arm work on it. The immediate focus will be Microscopic Imager images... lots of 'em.

Over on the other side of the planet, Opportunity is having a tougher time of it. Last week we got slowed down a little by some unexpected software issues. Those are cleared up now, and as of yesterday Opportunity was on the move again. But now we've got a new situation. After yestersol's drive, all six wheels we're dug pretty deeply into a large ripple. We've gotten dug in before and gotten out just fine, so this isn't cause for immediate concern. But we're likely to be here a little while, taking our time to get our wheels back on top of the soil again, and also taking some time to figure out what's different about this soil and how to keep this from happening again as we continue to work our way toward Erebus.

April 22, 2005

We've had a pretty amazing week with Spirit. With two nearly perfect drives we're now parked right in front of Methuselah, and this coming weekend we're hoping to take several hundred megabits of what should be some spectacular high-resolution Pancam images. It's too early to tell exactly what we're dealing with here, but the next week or so should reveal a lot. We're going to look the Pancam stuff over on Monday, pick our spot, and then move in close for some work with the instrument arm.

The really fun thing this week has been the dust devil movies we caught with Spirit... they're truly amazing. These things are big -- quite a few tens of meters in diameter -- and moving across the martian surface at a good speed. We've caught dust devils before, of course, but we'd never seen anything quite this spectacular until this week. It's the kind of surprise that makes this job a lot of fun.

What we still don't know is what all the dust devil activity has to do with the wonderful "cleaning events" that swept the dust off our solar arrays a few weeks ago. There were several cleaning events spread out over several sols, and it's hard to believe that we got hit by several dust devils... especially since all the dust devils we've seen have been out on the plains, while we're now well up into the hills. But we were parked right on the crest of Cumberland Ridge when the cleaning events happened, and if you've spent any time in the mountains you know that ridge crests tend to be windy places. So maybe we just caught some lucky wind gusts. One thing these dust devils make clear is that it's a windy time of year at Gusev crater.

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

This week we're reviving a feature of this site that was around for many years: updates from the principal investigator. I did these for quite awhile during the development of the mission, all the way up through launch and landing. Once we were on the surface of Mars, though, and we had what seemed like the whole world watching us, it seemed a bit less necessary to do these updates... there was already plenty of news out there about us. But now that the uproar has died down -- with the rovers still very busy on Mars -- it seemed like a good time to revive the tradition.

I don't know how frequently I'll manage to do these... with the rovers still active it's had to find time for anything but flight operations. I'll do my best, though, and I'll try to make it at least once a week.

For Spirit, the big news is that we've interrupted our climb of Husband Hill to take a look at a fantastic new outcrop that we've named Methuselah. We just spotted Methuselah this past weekend, in some Pancam images that we took on Sol 454. It's a spectacular outcrop of layered rock, perhaps the best that Spirit has yet seen. It'll take a few sols of driving to get to it, but once we're there we're expecting to work it over pretty thoroughly. After 400+ sols in Gusev crater we've finally started seeing some real stratigraphy, and we think that Methuselah may have some very interesting stories to tell.

The fun thing about Spirit lately has been that we've had so much solar power to play with. When we landed, Spirit's solar arrays were putting out about 900 watt-hours of power... that's enough power to run a 100-watt light bulb for 9 hours. By a couple of months ago, we were occasionally seeing numbers as low as 350 watt-hours, because of all the dust on the solar arrays. We think that the rovers can't survive at power levels much lower than 280 watt-hours. So we were having a tough time. But now, with the solar arrays cleaned off by the wind, we're back over 800 watt-hours! So Spirit is a very capable rover these days.

Over on Opportunity, I suppose the biggest news has been the trouble with the right front steering actuator. It stopped working a few sols back, and it may have failed permanently. This isn't nearly as bad as it sounds! The rovers have many possible steering techniques, and some of them don't require the steering actuators at all. And we caught a lucky break... the wheel is pointed very close to straight forward, which makes these alternative steering techniques pretty easy. So if we've lost this actuator, it's really just an annoyance, not a problem. It's a powerful reminder, though, that these rovers aren't going to live forever. We've been pushing Opportunity very hard, and we're going to keep pushing her.

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.

That's it for now. Stay tuned, and I'll do these updates as often as I'm able to.