Recent Comments From Steve Squyres, notes from his Houston, Tx presentation Options

[helvick]

For all that MER is a brilliant success, it's in many ways not so much a Rover as a fixed lander that can, er, move. A human being would be at the top of the hills before the first morning was half over... ...we're not exactly in the Himalayas, so need not be particularly worried about the terrors of the mountains!

All very true but this does emphasize how delicate and potentially fragile the little beasties are.

I wouldn't ignore the risk that there are significant variations in the dust environments on a small scale though. We saw that simply having Opportunity inside Endurance during the worst of winter kept it much healthier than Spirit and that situation changed dramatically once it came out of Endurance. I don't think altitude per se has anything to do with it - it seems to me that the localised behavior of the atmosphere at ground level is entirely dependant on the shape of the terrain. It would not surprise me at all to find that the other side of the hill was a deep dust drift that could cause Spirit lots of problems.

[RNeuhaus]

Sorry for the length of this post, but it seemed there was a lot that others would find interesting.  I hope I presented it accurately.

No sorry please, I would say to you "Many thanks", I am very pleased to hear from you.

Rodolfo

[RNeuhaus]

One factor that has to be considered is the increasing altitude of Spirit over the plains.  With such a thin atmosphere, there has to be a sharp drop-off in dust content even at the top of martian hills.  If this is a factor, it makes the thought of decending down the South side of the hill going into winter a more daunting one.

Yes, indeed I agree it. The higher land, there is less dust, less sand, more rocks, and more winds...

I think, the other good factor to build up the solar power is that Spirit spent almost all the time facing on the north side where the sun incidence is closer to 90 degree.

Rodolfo

[Deimos]

One factor that has to be considered is the increasing altitude of Spirit over the plains.  With such a thin atmosphere, there has to be a sharp drop-off in dust content even at the top of martian hills. 

Nope. The published (and conference abstract) observations have dust well mixed to 10 or 20 km, with some dust at more than 40 km. The dust size seems to get a bit smaller up high, but it's there.

There's a simple (or just simplistic) way to guess at this. Visibility is to optical depth 4 or so. If there are 10 optical depths of dust between you and a crater, you cannot see it. If there is only one, you can. Since optical depth straight up from the rovers is about 1 or so, that means whatever the dust scale height is, you can barely make out features about 4 times further away. So, if you can see 60 km, the dust scale height is 15 km; if the dust scale heght is 100 m (providing optical depth is 1-ish), then you can see <1 km.

The numbers are all rough, but the basic idea is that the dust cannot be confined low where it is between Spirit and hills visible to Spirit. +-100m means +-1% (ish) dust, not large percentage changes.

[babakm]

Nope. The published (and conference abstract) observations have dust well mixed to 10 or 20 km, with some dust at more than 40 km. The dust size seems to get a bit smaller up high, but it's there.

Did a bit of research on the subject and according to the latest research I could find (Forget et. al., 1999), the dust distribution in the lower atmosphere is indeed pretty uniform. Couldn't find anything concrete on particle size by altitude except that the stuff in the upper atmosphere is mostly of the 1-2 micron variety. I could still have a point, but I'll defer on this one for now.

[Bob Shaw]

Did a bit of research on the subject and indeed, according to the latest research I could find (Forget et al), the dust distribution in the lower atmosphere is pretty uniform.  Couldn't find anything concrete on particle size by altitude except that the stuff in the upper atmosphere is mostly of the 1-2 micron variety.  I could still have a point, but I'll defer on this one for now.

That stuff ain't 'dust' - it's practically *smoke*!

[Bill Harris]

That stuff ain't 'dust' - it's practically *smoke*!

I don't know how Stoke's Law applies in a very thin, very cold atmosphere, but I'd suspect that the dust is various oxides of iron and silica ground down to molecular levels. It would take millennia to settle. I suspect that there are a lot of larger particles near to the ground that are made airborne by the wind and more larger particles within centimeter saltating away.

With no water vapor and clouds the dust in the atmosphere is not washed out as it is on Earth.

--Bill

[edstrick]

Viking's landers and orbiters both observed the half-life <sort of> of dust in the atmosphere is a few weeks. Once the two great 1977 dust storms stopped raising dust and it got fairly uniformly mixed, there was a very nice exponential decay in observed dust levels. I'd have to dig out old xeroxes of articles to get hard numbers, but they got some very high quality science from the data. Dust smaller than the 1 to 2 microns of typical suspended dust may be present, but more likely as composite dust particles, instead of single grains.

[babakm]

A 1999 report with relevant data/theories on the subject here. Look at Table 3 (pressure) and Figure 3 (dust). They both imply pretty uniform dust levels in the altitudes that we're talking about. I'd love to see the "ground truth" results from the MER/MEX join observations.

[helvick]

From page 187 of Squyres' book, Roving Mars:
"If we launched in 2005, we'd arrive at Mars when the planet was far from the sun and when it was almost as far away from Earth as it ever gets. Solar power would be bad, and communication to Earth would be awful.  The mission was so bad in 2005 that it wasn't clear that it made sense to fly it at all."

It would be amazing if the rovers lasted into spring of 2006 when the mission prognosis for that time was so bad, even for a freshly delivered rover. To think that at least one of the rovers may end up doing just that boggles the mind!

The 2003 launch window meant landing in Jan 04, that had insolation levels for the 90 Sol primary mission at levels that would produce ~840 Watt hours on average (ignoring varying tau, dust loss etc). Light time went from ~ 9 minutes at the start to 16minutes at the end.

For the 2005 Launch window (the one MRO used and assuming a 7 month flight time) insolation would have produced about ~720 watt hours on average during the primary mission and light time would have increased from 12 to 19 minutes over the 90 Sols.

[chokai]

I saw SteveS yesterday in Seattle. I can highly recommend going to see him if ya get the chance. The book is great (stayed up all night reading it when I got it) and his presentation on the rovers is filled all sorts of great tidbits, and you always get new tidbits from him every time from what I heard about the one at Microsoft later that day. Showed some great stuff including some amazing dustdevil footage I had not seen yet. He mentioned the IMAX movie and seemed to indicate he was involved at least somehow, but I was unable to ask him about his involvement in that film as he was running out the door to get to his next engagement.

A few good jokes too showed the sense of humor Steve has that we've all come to appreciate. I personally enjoyed his comparison of the Rovers to Magellans expedition. Where Magellan started out with 200 men and only 18 survivors finished. And SteveS observed that he is going to finish his mission with the 18 surviving grad students.

[CosmicRocker]

How fortunate. It sounds as if you were able to catch him in two different shows on the same day. (or perhaps you heard about the the one at MS second hand.) Anyway, did he have anyting interesting to say about the most recent sols?

[chokai]

I only caught him at one presentations. Heard about the other one through friends who work at the Evil Empire that just had a few little differences, different factoids and the like. He did not say much beyond the recent sols that was not covered in his recent post. Fully expects to take "the mother of all panoramas" from the top of Husband Hill, I would say he is very confident in the ability to summit. He reiterated that they expect to summit and then drive down the other side, no indication to any planning changes. He didn't have much to say about Oppy.

I do regret not getting to ask him about any new conclusions about the state of Spirit's RAT though, given the pictures they took a few weeks ago on sol 565.

And Steve did show a video made of the dust devils recorded by spirit on Sol 568 that is very impressive. (It's Friday I had time to surf this evening, and find the originals.)

[djf]

Here's a recently posted transcript from an Australian radio show called "The World Today" with Steve as a guest.

Not too much new, but he mentions his initial reaction to the first navcams from the top. The transcript gets the spelling of his surname incorrect, but the interview itself is fairly good for a general audience show. Eleanor Hall is apparently ABC's answer to NPR's Terry Gross. ;)

STEVE SQUIRES: We expected them to last at least 90 days. Today is day 583 of our 90-day mission to Mars and they're still going strong. In fact, Spirit just today, arrived at the summit of a mountain that we had been climbing on Mars for the past year – I just saw the pictures from the summit about 10 minutes before we began this interview.

ELEANOR HALL: And how exciting were they? 

STEVE SQUIRES: Oh, it was fabulous. Good heavens! Spectacular views in all directions - we've only taken some low-resolution black and white pictures so far, but we're going to take the mother of all panoramas from this spot. It's going to be absolutely amazing.

[djellison]

  The transcript gets the spelling of his surname incorrect,

I was spelling it as Squires for 15 months before figuring it was Squyres

Hopefully I'll be skipping over most of those sorts of questions - straight down to the good stuff

Doug