Stuck in the sand - a long way from anywhere

 

The image above is a geologist’s bad dream, the vehicle’s wheel churning uselessly in the sand. But this is also NASA’s bad dream, for the vehicle is Spirit, one of the tenacious and hard-working Mars Rovers that have been trundling around the red planet for five years more than they were expected to. Spirit had suffered a front wheel failure some time ago, so has been driving backwards ever since, dragging the non-rotating wheel behind it. But now Spirit is stuck in the sand – and look at how stuck that wheel is and how powdery the sand is. "Spirit is in a very difficult situation," JPL's John Callas, project manager for Spirit and its twin rover, Opportunity, said. "We are proceeding methodically and cautiously. It may be weeks before we try moving Spirit again. Meanwhile, we are using Spirit's scientific instruments to learn more about the physical properties of the soil that is giving us trouble." The project team are building a sand-filled replica model to experiment with possible solutions, but looking at that image, you can just feel the predicament. And then there is a concern that the rover has dug itself in so far that the chassis is high-centred - stuck on an underlying rock (I sympathise – been there, done that – but not on Mars).

For the early Mars landing missions, NASA sought the expertise of Ralph Bagnold (see my post on The Man who Figured Out how Deserts Work) and it was Bagnold who pioneered desert motor vehicle travel. Among his many contributions were, of necessity, ways of extricating oneself from soft sand. He started out using rope ladders (see illustration at left, below) to help his Model T and Model A Fords continue on their way, but he then hit on the idea of using lengths of metal roofing material (below, right) that evolved into the lightweight aluminium sand tracks that we use today.

 

I was personally grateful for this innovation on any number of occasions during our retracing of Bagnold’s 1938 Western Desert Expedition a couple of years ago. However good the driver, and however fast you drive over firm sand (with dramatically deflated tyres), there comes a point when the fickle and unpredictable behaviour of granular materials will do you in. A couple of examples below, the modern versions of Bagnold’s sand tracks being put to use on the left. An aside on the photo on the right: we were fortunate to have several women on the trip, two of whom were named Jane. The substantial lady in the foreground is one, and our Egyptian crew decided to distinguish between the two by naming one “Jane” and the other “Double Jane.” Double Jane, thank heavens, thought this was hysterically funny.

And all of this reminds me of a movie I recently watched on DVD – Japanese Story. This is ultimately a tragic tale, but I was for a while entertained by a female geologist (Toni Collette) in a leading role (a rare event, male or female). This is the movie in which, on being required to  act as chauffeur for a visiting Japanese investor in the Australian mining operation she works for, she delivers with fervour the classic line “I’m a bloody geologist, not a geisha!”  I soon began to realise, however, that the makers of the movie had not bothered to talk to a real geologist to figure out how this character might behave (she took no notice whatsoever of fantastic outcrops she was driving past, for example). But the ultimate absurdity was when she got her truck stuck in the sand. She revved the engine and tried to drive forward, all the time embedding the rear wheels up to the axles. Now I have a habit (which, yes, I am completely aware is pointless) of shouting at the TV, and I found myself hurling advice. But to no avail. She subsequently burnt out her winch trying to use a sand anchor. Now I appreciate that this scene was necessary for the dramatic progression of the story line, and the these two people had to spend time together marooned in the desert. But did it have to be at the cost of making geologists look incompetent?

Spirit could use help from Ralph Bagnold more than Toni Collette.

[Spirit image courtesy of  NASA/JPL-Caltech; see New Scientist article here; Ralph Bagnold photos by kind permission of Stephen Bagnold]

Comments

[Jules]

Great post(s)as usual Michael. I was listening to National Public Radio's Science Friday recently and a scientist from NASA explained that they are studying the possibility of using the Rover's arm to sort of "pole vault" the vehicle out of its predicament. The arm was not designed for something like this, but they may give it a try by using it as a method to lift the Rover out of the sand as sometimes a construction backhoe driver would do by putting their scoop down hard in the soil and using applied pressure to swing them up and out of a pit thay have sunk into.

Welcome back to the States.

Cheers :)

[Michael Welland]

Hi Jules - thanks for the update - that's a fascinating and creative way of solving the problem. But the very idea of managing such an operation on Mars does boggle my mind!

[Jules]

I can imagine that NASA scientists will be sweating nervously also since it takes an average of 13 minutes for a radio signal to reach Earth so they will know if the maneuver was successful!