Vesta asteroid shows shadowed top

The latest image was acquired last Saturday, and was taken from a distance of about 5,200km

Nasa's Dawn spacecraft has returned a view of the giant asteroid Vesta's northern hemisphere.

The spacecraft acquired the image after making its first pass over the dark side of the rock since going into orbit two weeks ago.

Vesta's northern polar region is currently in the deep shadow of winter.

Dawn's best look at some of the surface features hidden in the picture are unlikely to come until the probe departs the rock in a year's time.

By then, Vesta should have shifted on its axis sufficiently to allow the Sun's rays to fall across some of its high-latitude mountains, valleys and craters.

"The north pole is in shadow now and when Dawn leaves it will be slightly illuminated," explained Prof Ulrich Christensen, from the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany.

"We may get a glimpse of some features currently in darkness, but with the Sun still very low on the horizon lighting conditions may not be ideal," he told me.

In the meantime, there is plenty to occupy the Dawn team, which promises to deliver its first interpretation on Monday of some of the features seen in the earliest imagery.

Nasa has scheduled a media conference with the leading scientists at its Jet Propulsion Laboratory in California. A parallel conference will take place in Germany, reflecting that country's key participation in the mission. The framing camera system was developed by the Max Planck Institute.

It is hoped the researchers will show us not just more pictures on Monday, but some colour ones as well. The framing camera system has a number of colour filters.

The mission's chief scientist, Dr Chris Russell from the University of California Los Angeles, told the BBC last week that the team had seen quite deep colouration in places - strong oranges and blues.

Ever closer: Last week's image release highlighted the southern pole from a distance of about 10,500km

Dawn entered into orbit around 530km-wide Vesta on 17 July, and will spend 12 months studying the rock before moving on to the biggest object in the asteroid belt between Mars and Jupiter - the dwarf planet Ceres.

Both objects should have something to say about the earliest days of the Solar System. Scientists often describe asteroids as the rubble that was left over after the planets proper had formed.

I have to say, the Dawn mission has got me very excited. If you think about it, it's a while since we've seen a new world up close like this. Rosetta's pass of Lutetia last year was spectacular, but fleeting.

And even the major Saturnian moons encountered by Cassini this last decade had some half-decent imagery associated with them before the joint Nasa/Esa/Asi mission turned up.

Vesta seems very fresh, and Ceres should be even more remarkable.

Ceres, of course, will become the first dwarf planet to be visited by a spacecraft - before even Pluto can be passed by Nasa's New Horizons probe. That rendezvous is not due to occur until 2015.

Someone has just asked me in the office how long we can keep talking about new pictures from Dawn at Vesta. The inference being: it's just a big hunk of rock. A while yet, I'd say.

There's a certain fascination with asteroids. That's borne out by Thursday's news about an 200-300m-wide asteroid not far from Earth that is moving in the same orbit around the Sun. It proved to be the day's most read story on the BBC News website.

Dumb, dull rocks? I don't think so.