The Mars rover Spirit is now within a few hundred metres of the hills it has been trundling towards since March.
Images of the Columbia hills suggest there may be outcrops of layered rock to examine, as well as many large boulders.
鈥淭his is the first time we鈥檝e ever had a close look at hills on Mars,鈥� said James Rice, of Arizona State University, Tempe, and a member of the rovers鈥� science team. In 1997, the Mars Pathfinder rover landed about 1000 metres from hills, but did not go closer.
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The hills are a tantalising target for the science team as they may hold different types of rocks to those already seen, which could reveal more about Mars鈥檚 geological history. 鈥淭hese rocks are much older than what we鈥檝e been driving across,鈥� Rice said at a press conference at NASA鈥檚 Jet Propulsion Laboratory on Wednesday. 鈥淭hey may be some of the oldest material ever seen on Mars.鈥�
The hills rise about 100 metres above the plain Spirit is on, and feature spurs and talus slopes of rock debris. The hills could have been formed by a number of phenomena 鈥� volcanic activity, rock deformation or meteorite impact. Spirit is likely to take about a week to travel the last 400 metres.
Computer reboot
But the rover鈥檚 journey has not been trouble-free. In May, the robotic rover suffered two unexpected computer reboots triggered by software glitches.
鈥淲e had bad luck to hit two very unlikely scenarios just eight days apart, but in both cases the software team was able to figure out the problem within a day,鈥� said Joe Snyder, a Lockheed Martin software engineer on the rover team at JPL. Spirit suffered serious software problems in January, just a few weeks after landing.
The onset of the Martian winter is also posing challenges. Lower temperatures, shorter days and the steady accumulation of dust on solar panels are gradually reducing the amount of work each rover can accomplish.
Spirit鈥檚 twin, Opportunity, has been hardest hit. It has been plagued throughout the mission by a heater switch that is stuck in the on position, draining away its power.
Deep sleep
So mission managers now place it in a deep sleep mode each night, which cuts off power to the main electronics systems including the heater.
This has doubled its useful daily work time to over four hours but has endangered one of the rover鈥檚 most productive instruments, the mini-Thermal Emission Spectrometer, which analyses rocks.
Without heating, the instrument is unlikely to survive temperatures lower than -50 掳C. Night time temperatures have already dropped to -46 掳C. As the winter advances, the scientists expect to lose the instrument.
In the meantime, Opportunity is using its microscope to analyse the texture of rocks on the edge of the stadium-sized Endurance Crater. The rocks appear similar to those seen at the rover鈥檚 landing site, but one, dubbed 鈥淧yrrho鈥�, has a braided ripple pattern.