快猫短视频

NASA鈥檚 Opportunity rover has seen its grandest vista yet and has likely reached the site of its final resting place. After a 21-month trek across a sometimes treacherous Martian plain, the rover has now wheeled up to the yawning chasm of Victoria Crater, its long hoped-for destination and the most important geological feature by far within 10 kilometres of its 2004 landing site.

鈥淰ictoria Crater is even richer than Endurance, with enough geology to occupy the rover for the rest of its operational life鈥�

快猫短视频s were electrified by the first high-resolution images of the crater wall, which includes a craggy outcrop dubbed 鈥淐abo Frio鈥�. The cliff stands almost three times as high as the 7-metre outcrop Opportunity left behind at Endurance Crater nearly two years ago 鈥� and so represents a correspondingly larger slice of Martian geological history.

Opportunity has also been spotted by the Mars Reconnaissance Orbiter, the latest arrival at the Red Planet, which photographed the rover perched near the cliff edge on 3 October, with even its tracks across the dusty plateau visible (see above). 鈥淭hat image, with that little rover parked at the top of that cliff, is one of the most evocative images I鈥檝e seen from all of planetary astronomy,鈥� says rover chief scientist Steven Squyres of Cornell University, New York state.

The rim of the heavily eroded crater, which is about 750 metres across, has a scalloped edge made up of dozens of rocky points with high, steep faces and deep alcoves between them, some of which have shallow, gentle slopes. The pathway downwards looks inviting 鈥� though perhaps deceptively so. On a firm surface, the rover can easily tolerate slopes of 20 degrees or more, but if the slope is composed of loose, dusty material the wheels could slip and the rover might be unable to exit. 鈥淚鈥檓 not eager to make a suicide dive,鈥� Squyres says.

The rover鈥檚 two cameras, set 30 centimetres apart, are too close together to give the depth information needed to assess the descent. So instead of plunging in, the rover team has sent Opportunity on a traverse along the edge of Victoria. Combining images from two locations should give the team a better sense of the depths and angles involved. The first full panoramic image, taken upon arrival at an alcove called Duck Bay, is now being radioed back to Earth 鈥� a process that will be interrupted for nearly two weeks as Earth鈥檚 orbit takes it behind the sun. During the break Opportunity will acquire a second full panorama from its new location on Cape Verde.

It is already clear that there are at least three different geological units exposed in the bedrock layers, Squyres says. In Endurance, all the rocks examined were within the topmost of these units, while just a glimpse of the next lower unit was visible. At Victoria the upper units 鈥渁re pretty massive, and we suspect are very finely layered鈥�, he says. Below that, there鈥檚 a layer with distinct cross-bedding, suggesting that it may have formed from wind-blown dunes. And below that, Squyres says, 鈥渢here鈥檚 an abrupt transition to something else鈥�, though that lowest unit was mostly viewed in shadow, and is therefore hard to identify.

Shortly after landing, Opportunity provided the first solid evidence for past water on Mars when it examined a much smaller outcrop conveniently located beside its landing site. This kept the rover busy for weeks, and its subsequent exploration of Endurance took months. Victoria is even richer, with enough geology to occupy it for the rest of its operational life.

Although Opportunity is in good health, both it and its twin rover, Spirit, have survived more than 10 times as long as expected and could expire at any moment. Faced with an uncertain but diminishing future, scientists may be inclined to take greater risks with the rover than they have in the past to maximise the scientific return.