LONG before the Mars rover Spirit turned around and rolled off its ramp, and even before it had taken the full infrared panoramic image that was supposed to be the most important tool for choosing which areas to visit, the scientists planning its mission had decided where they ultimately want their Mars buggy to go: the hills.
The very first panoramic image taken after Spirit landed, even in low-resolution black and white, made the choice clear. Tantalisingly nearby on the horizon was a long, low set of hills bearing intriguing dark markings and layers of rock.
Images taken from orbit have shown that layering is widespread on Mars. But this would be the first chance to get a close look and analyse the layers with colour filters and infrared spectroscopy. That might finally reveal what the light and dark bands are made of, and how they were deposited. That, in turn, just might be the key to understanding Mars鈥檚 complicated climatic past.
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The target is 2.5 kilometres away 鈥� far beyond the rover鈥檚 nominal range of 600 metres. But if all goes well Spirit has a chance of making it by the end of its mission. Simply getting closer to the hills could be enough to provide significant new information.
The desirability of reaching the hills is one of the few things that the diverse group of scientists involved in Spirit鈥檚 mission actually agree on. The past week at mission control in Pasadena, California, has seen a lively series of discussions about exactly what kind of environment Spirit is sitting in, and how best to find out.
Some of the scientists firmly believe the site is the dried-up bed of an ancient lake. Others think it consists of layers of volcanic ash and basalt, as most of the Martian surface appears to be. Alternatively the plain鈥檚 original materials could have been scoured away by millions of years of fierce winds, leaving remnants of some very ancient surface. Or it could have been formed by the movement of glaciers.
Each position has its advocates, and the focus now is on carrying out tests that will rule out any of these options or, if the team gets really lucky, clinch one of them as being right. 鈥淲e鈥檙e not going to find out until we start pushing rocks around,鈥� says team member and geologist Michael Carr. The texture of the rocks will be important: rocks made of smooth, round grains are likely to be sedimentary, indicating the presence of flowing water, while rough or jagged ones are probably volcanic. Rocks that are layered, especially if the layers sometimes form ripples, suggest a marine environment.
But one of the most promising tools on board Spirit is its spectrometer, which identifies specific minerals rock by rock from their infrared emissions. Readings taken from the rover鈥檚 landing site have already indicated that there are carbonates, and possibly hydrated minerals, which are among the most sought-after signs of past liquid water.
As 快猫短视频 went to press, the rover was scheduled to roll off its platform and start exploring on Thursday morning, GMT. Phil Christensen, designer of the infrared spectrometer, can hardly wait. 鈥淲e鈥檒l have a field day,鈥� he says.
