Although the team at the Ludiver observatory at La Hague, near Cherbourg on the Normandy coast, were mounting a continuous Mars-watch, they also hooked up a simple off-the-shelf webcam to their 60-centimeter optical telescope.
The result, according to observatory manager Bruno Daversin, was a photo of "exceptional quality," caught overnight on Saturday and transmitted to the observatory's web site at www.ludiver.com.
The webcam -- a simple electronic video camera that feeds its images directly into a computer -- was "a treasure of innovation and performance," said Daversin, who in addition to running his observatory is head of an image acquisition group in the French Astronomical Society.
The device, placed simply below the telescope's viewing apparatus, allowed him to snap 30 images per second, and to process and even merge them on his computer, he said.
Coupled with the team of five enthusiasts who have been keeping watch at the observatory over recent nights, adjusting the telescope and looking for the perfect break in the clouds, the camera provided better monitoring than much more expensive devices, he said.
"Around midnight on Saturday evening there was mist over Cherbourg, but when we went up to the observatory we were just above it, and for around half an hour we had absolutely exceptional conditions of transparency," Daversin said.
On the prized picture, a computer-enhanced composite of the 1,000 best images out of 2,000 caught by the camera at the time, "you can distinguish details of around 30 kilometers (18 miles) wide, including the icecap on the south pole, which is melting during the Martian summer," he enthused.
"Normally, out of 2,000 images of Mars, you would only get 200 clear ones," he added.
Alain Cirou, head of the French astronomy magazine Ciel et Espace, agreed that the picture taken by the Ludiver observatory was "of exceptionally good quality."