Emily over at the Planetary Society blog is often full of wisdom, and I’m impressed she managed to keep calmer that I did when faced with ’Bigfoot’ on Mars. (It’s STILL a rock!) She says :

You may find it annoying that after months of virtually ignoring the rover missions, there is finally a much-discussed news story, and it’s on something as silly as a humanoid-shaped rocky outcropping — but please suppress your annoyance and try to use this as a teaching moment.

Well, yes, that’s what I wish the BBC had done, but let’s have another look at that picture. Not the close-up (it’s a rock!), but the panorama. What do you see if you look at it with an astronomer’s eyes? (Sadly, not a planetary geologists eyes, but you can’t have everything).

The first thing I noticed was how dusty the solar panel visible at the front of the picture was (the first clue that the picture was from late in the mission, not from 2004 as was widely reported). Spirit relies on these panels to get the energy it needs to keep itself alive. The Martian nights are cold (too cold for even Bigfoot, I would guess) and without enough energy to heat itself the rover’s electronics will stop working. Dust on the solar panels has always been a good bet for what will kill the rovers eventually; they had some respite when a freak gust of wind cleaned the panels but things are obviously still pretty bad.

Actually, that’s the reason Spirit’s here at all. Mars is tilted on its axis by almost the same amount as the Earth, and so has seasons just as we do. It’s heading toward being winter for Spirit, and that means short days, long nights and little Sun, just as it does for us here in England. Spirit’s driven back to this point, near a place called Home Plate, where it can tilt its dust-encrusted solar panels toward the Sun and hope to wait out the worst of the winter.

Now what about the landscape? There are hills on the horizon, not the Columbia hills Spirit has been exploring as part of its role as the first Martian mountain climber – they’re off to the right – but a reminder that Mars is a world. No matter how much longer Spirit lasts, it’ll never explore these distant features but they’ll be waiting for us.

There are plenty of features nearby to keep us busy in the meantime. The rocks are weathered, I would say, but not by the action of water – this isn’t an old Martian river bed. The weird structures, including Bigfoot (it’s a rock!) are probably the result of erosion by either local or large scale dust storms, like the one that engulfed Mars last year. Sand carried by wind can be quite abrasive – a natural sandpaper, if you like.

Excitingly, many of the rocks seem to have layered structures (see, the close-up is useful for something after all). That suggests to me that they are sedimentary rocks, with each successive band laid down by successive flooding. Even if that’s not true, the presence of layers gives us the prospect of reading these rocks as a history book, working backwards through Mars’ past. If there was ever water in large quantities here, the minerals in these rocks might hold the evidence.

It’s hard for me to forget the bigger picture, too. This is a place, and a view, that Spirit was never meant to see. It travelled long and hard to get here, surviving long past the 90 days it was designed to last. The least we can do is appreciate that the rovers are still working; Emily gets it right once again:

While they’re still there, we should do them the honor of thinking of them every day, checking on the results of their daily toil, because one day all too soon they’ll both fall silent, never to be heard from again..

You can follow the exploits of Spirit and Opportunity at their JPL Home Page, or for the dedicated at Doug Ellison’s excellent Unmanned Spaceflight message board.

Update: I decided the occasion needed marking.