MPL "Landing" Site Identified??

Palomar · 2005-05-06 06:11:32

*They think it may still be in 1 piece -- nearly intact. :-\ In the south polar region. Didn't want to put this in REB's MOC thread, thought I'd start a new one. And of course the mission failed prior to this ikonboard being created (no prior thread).

According to a statement on MPL from Malin Space Science Systems, the MGS photo shows brightness of a candidate "parachute" unfurled on Mars. In addition, the MPL candidate location image also shows a brightness difference in the martian terrain -- conceivably mussed up by the lander’s engine blast.
Sitting in the center of that disturbed surface is a small, bright spot – ostensibly the one and only, but long silent: Mars Polar Lander.
...the probe’s deployment of landing legs sent a faulty message to onboard software suggesting that touchdown had occurred. That flawed signal, it was later deduced by a troubleshooting team, likely shut down the Mars Polar Lander’s engines prematurely.
The craft then free fell to Mars and became damaged goods on the distant planet.

--Cindy

Palomar · 2005-05-06 10:20:39

http://www.universetoday.com/am/uploads … l.jpg]NICE collection of photos

*...with many designations. This has MUCH better detail than the Images available in the first article I posted.

Found at http://www.universetoday.com/am/publish … 52005]this related article.

Additional, higher resolution images will be taken by MGS later this year to confirm the discovery.

...the software stopped the engines as soon as the check was made, about 28-30 seconds into the 36-40 second burn. MPL was probably at an altitude of about 40 m, from which it freely fell. This is equivalent to a fall on Earth from a height of about 40 feet.

Hmmmmm.

--Cindy

Shaun Barrett · 2005-05-06 20:01:54

Very interesting stuff.
I'm a little bit puzzled, though.
If the rockets shut down some 40 metres above the surface, why is there such a distinct darkening of the soil around the probe, which has been attributed to rocket exhaust?
It seems unlikely to me that the rocket exhaust could have affected the surface from 40 metres (130 feet) away. In such a thin atmosphere, the plume would surely have dissipated sideways within a very short distance of the rocket nozzle(?).
Shouldn't the surface be undisturbed?
???

SpaceNut · 2005-05-06 20:08:49

Or did the craft think that it was 40 meters still to go but with the thinner air was actually on the ground with its engines still running full throttle.

Rxke · 2005-05-07 02:33:00

Shaun, wouldn't it be the other way round, that the thin atmosphere makes it easier for the blast to reach the surface? 40 metres sounds a lot, but the retro rockets are not children's toys either, they have to do a lot of braking, so I'd gather the exhaustplume would be quite big, ever saw the excellent animation about the MER's landing? the braking/rockets seemed impressive enough, heehee.

SpaceNut, I read somewhere the acellerometers could be to blame but for another reasoon; when the landing legs deployed, the brusque movement led the craft to think it actually landed ??? So it shut off its engines (hard to believe)

GraemeSkinner · 2005-05-07 07:33:19

My first thought when I looked at the image was that neither the chute or the retro's had provided sufficient braking and that the dark patch was a small crater. But thinking about it the retro's make a lot more sense as it looks like the lander is in one piece.

I'm surprised the 'chute has not blown away by now though.

Graeme

Palomar · 2005-05-07 09:35:21

I'm surprised the 'chute has not blown away by now though.

*Just curious: How much would a parachute for a lander of that sort weigh? And might it have metal attachments to it (on the ends) which might further weight it down?

--Cindy

Shaun Barrett · 2005-05-07 18:19:26

Rik:-

Shaun, wouldn't it be the other way round, that the thin atmosphere makes it easier for the blast to reach the surface? 40 metres sounds a lot, but the retro rockets are not children's toys either, they have to do a lot of braking, so I'd gather the exhaustplume would be quite big, ever saw the excellent animation about the MER's landing? the braking/rockets seemed impressive enough, heehee.

I didn't know much about the characteristics of rocket plumes in a vacuum until I read the scientific refutation of the "Apollo Moon Hoax" nonsense. One of the points made by the conspiracy theorists was that the Descent Module rocket didn't produce a crater and didn't really leave a very prominent blast mark either. (Naturally, these fools deduced that this helped to prove the lunar landings never took place. )
Anyhow, the explanation of the lack of significant scarring of the surface by the LM's descent-stage rocket included information I think is useful in evaluating the effect of the MPL's retro-rocket.
I found http://www.badastronomy.com/bad/tv/foxapollo.html]THIS SITE, which includes the following about the LM's landing rocket:-

They fired the rocket hard to deorbit and slow enough to land on the Moon, but they didn't need to thrust that hard as they approached the lunar surface; they throttled down to about 3000 pounds of thrust.
Now here comes a little bit of math: the engine nozzle was about 54 inches across (from the Encyclopaedia Astronautica), which means it had an area of 2300 square inches. That in turn means that the thrust generated a pressure of only about 1.5 pounds per square inch! That's not a lot of pressure. Moreover, in a vacuum, the exhaust from a rocket spreads out very rapidly. On Earth, the air in our atmosphere constrains the thrust of a rocket into a narrow column, which is why you get long flames and columns of smoke from the back of a rocket. In a vacuum, no air means the exhaust spreads out even more, lowering the pressure. That's why there's no blast crater! Three thousand pounds of thrust sounds like a lot, but it was so spread out it was actually rather gentle.

This is what led me to think the MPL's rocket, if it cut out at 40 metres altitude, in what is effectively almost a vacuum, wouldn't have left such a prominent dark marking on the Martian surface.
It looks to me as though the rocket kept firing all the way down.
Does anyone agree ... or have I erred somewhere in my logic on this? ???

dicktice · 2005-05-07 18:46:19

Nope. If you watch and listen to the landing sequences in each of the Apollo missions, in "From Earth to Moon," they shut down after making contact. Wouldn't you?

Shaun Barrett · 2005-05-07 21:15:08

Hi Dicktice.
Can it be you've missed the point?
The LMs did indeed keep firing their descent engines until contact with the lunar surface was made. The question here is whether the Mars Polar Lander's engine shut down 40 metres above the Martian surface.
NASA is suggesting it did but I'm wondering whether the markings on the surface indicate otherwise. ???

GregM · 2005-05-07 22:11:56

A few things on this:

1)Most Apollo LM decent engines were in fact shut down when the engine was still about 2-3 meters from the surface. If you look carefully, you will notice long, wire-like extensions coming out of the bottom of the LM footpads. These were contact sensors. When one of them sensed contact with the lunar surface, a light on the control panel inside would activate, and the Commander would then manually shut off the decent engine at that point. The LM would literally fall to the surface from that point on. If you watch the films of the powered descent taken out of the LM window, you can actually see the fall and jolt in the last few seconds. In Apollo 11, you can actually hear Aldrin call out “contact light” just prior to touchdown - this is the tip of a probe scraping the surface - not a landing pad.. On a few occasions, the Commander did keep the power on till touchdown, but most did not.

2)One thing about dust in a vacuum is that it behaves quite differently. It flies away very easily at almost no urging. It really takes a very minimal pressure to stir things up. Although we like to think of Mars’ atmosphere as being more significant than it really is, we have to remind ourselves that it isn’t, and is in fact closer to a vacuum. It is not implausible that rocket engines could stir up surface dust at that distance whatsoever. The explanation of the low PSI of a decent engine is correct, think of it more liike a very, very strong breeze. To shoot a hair dryer at a half inch layer of dust from 3 or 4 meters away would be a better Earth-based analogy of what happens in a vacuum. Stuff still goes flying everywhere despite the relativly low pressure.

3) Lastly, the images from MSS are EXTREAMLY processed. The disturbed soil really isn’t that dark, compared to the surrounding soil. It is slightly darker in reality. As an example of a similar situation check this out:

http://www.hq.nasa.gov/alsj/a15/as15p93 … 377det.jpg

This is Apollo 15 on the Lunar surface. You can actually see the LM shadow. The heavy image processing brings out the contrast differences between the undisturbed soil and the soil disturbed by the descent engine during touchdown. The contrast difference really isn’t that extreme in reality (just look at images taken on the surface - the ground isn't really white). The heavy image processing is however, very useful in identifying the landing location.

They have probabally found MPL. The main body is likely in one crumpled piece, with small bits scattered around it.

Shaun Barrett · 2005-05-07 23:52:58

Thanks, GregM.
This is the kind of discussion I was trying to elicit. I note your opinion that the MPL's rocket exhaust, even though widely spread in the near vacuum of Mar's atmosphere, would still have no trouble at all disturbing dust on the surface from 40 metres up.
I confess, though, I'm still having trouble visualizing that scenario because the darkened surface patch in the image (whether it's actually that dark or not) seems so tightly constrained to the immediate vicinity of the crashed probe itself.
But, then, what do I know about the behaviour of rocket exhaust in such circumstances? All I can do is express an opinion.

Any other opinions on this?

srmeaney · 2005-05-27 03:50:39

Kewl! At last they can find you on Mars. I'm sure the first colonists will be thrilled that they can be on 24 hour TV every time they are out doors.

The http://news.bbc.co.uk/nol/shared/spl/hi … /1.jpg]BBC Landing images

Hi Dicktice.
Can it be you've missed the point?
The LMs did indeed keep firing their descent engines until contact with the lunar surface was made. The question here is whether the Mars Polar Lander's engine shut down 40 metres above the Martian surface.
NASA is suggesting it did but I'm wondering whether the markings on the surface indicate otherwise.

They may not have cut out at 40m The soil disturbance looks a little like a fail at or after landing.

Shaun Barrett · 2005-05-27 05:37:56

Thanks for this picture, Sean:-

It's interesting to observe the shape of the darker surface material, which I assume is the actual rocket blast zone(?). And note the scale - which appears to be 2 metres per millimetre.
From these two pieces of information, we can see that the rocket 'scar' on the surface is elongated and covers a region some 18 metres long but no more than 6 metres wide.

Is it possible the MPL was coming in on an angle, with too much lateral velocity? Could it be that, rather than cutting out too early, the engine burned all the way down, as planned, but the unintended lateral velocity caused the lander to pitch over on contact and sustain terminal damage? ???

Palomar · 2005-10-19 06:04:34

To answer the original question

*Nope. Lander is still "lost." Apparently further search is impossible (scheduling and time constraints).

--Cindy

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#1 2005-05-06 06:11:32

Re: MPL "Landing" Site Identified??

#2 2005-05-06 10:20:39

Re: MPL "Landing" Site Identified??

#3 2005-05-06 20:01:54

Re: MPL "Landing" Site Identified??

#4 2005-05-06 20:08:49

Re: MPL "Landing" Site Identified??

#5 2005-05-07 02:33:00

Re: MPL "Landing" Site Identified??

#6 2005-05-07 07:33:19

Re: MPL "Landing" Site Identified??

#7 2005-05-07 09:35:21

Re: MPL "Landing" Site Identified??

#8 2005-05-07 18:19:26

Re: MPL "Landing" Site Identified??

#9 2005-05-07 18:46:19

Re: MPL "Landing" Site Identified??

#10 2005-05-07 21:15:08

Re: MPL "Landing" Site Identified??

#11 2005-05-07 22:11:56

Re: MPL "Landing" Site Identified??

#12 2005-05-07 23:52:58

Re: MPL "Landing" Site Identified??

#13 2005-05-27 03:50:39

Re: MPL "Landing" Site Identified??

#14 2005-05-27 05:37:56

Re: MPL "Landing" Site Identified??

#15 2005-10-19 06:04:34

Re: MPL "Landing" Site Identified??

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