Named by the Romans after the fleet-footed messenger of the gods, the planet Mercury is closest to the Sun. Seen here by NASA's Messenger spacecraft on 14 January, this observation was the first of its kind since the planet was glimpsed by Mariner 10 in the 1970s.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
SYDNEY: In a successful flyby, NASA's Messenger probe has captured some of the most detailed pictures yet of Mercury's surface – and they offer new insights into the planet's geological past.
As the spacecraft approached Mercury on 14 January, its narrow-angle camera captured this view (see picture, right) of the planet's rugged, cratered landscape, illuminated obliquely by the Sun.
Geological features
This image was taken from a distance of around 18,000 km, 56 minutes before the probe's closest encounter with the surface. It shows a region roughly 500 km across, including craters as small as one kilometre wide.
The large, shadow-filled, double-ringed crater to the upper right of this image was first glimpsed by NASA's Mariner 10 spacecraft more than three decades ago and named Vivaldi, after the Italian composer – but Messenger has recorded it in much greater detail.
The crater's outer ring has a diameter of about 200 km. Messenger's modern camera has revealed features including a broad, ancient depression overlapped by the lower-left part of the Vivaldi crater.
A team including NASA and John Hopkins University scientists are in the process of evaluating additional images snapped from even closer range, which show features on the side of Mercury never seen by Mariner 10.
Mariner 10 made three passes of Mercury in the mid-1970s - but the same side was illuminated by the Sun on each of those occasions, meaning it could only map 40 to 45 per cent of the surface.
Advanced technology
In a statement, they said "it is already clear that Messenger's superior camera will tell us much that could not be resolved even on the side of Mercury viewed by Mariner's vidicon camera in the mid-1970s."
NASA added that images such as this can be read in terms of a sequence of geological events and provide insight into the relative timing of processes that have acted on Mercury's surface in the past.
Messenger is scheduled to fly over Mercury again in October 2008 and September 2009, then return for a final sweep in 2011 when it will enter Mercury's orbit for a year-long study of the planet.
The spacecraft has already flown once past Earth and twice past Venus since its August 2004 launch. It will have travelled 7.8 billion km when it completes its six-and-a-half-year odyssey.
with John Hopkins University Applied Physics Laboratory and NASA
