Isidis Planitia is probably a very ancient impact basin caused by the collision of a comet or a 50 km diameter asteroid onto the surface of Mars about 3-4 billion years ago. Subsequently its floor may have become flooded by volcanic lava before being further buried by sediment derived from the surrounding highlands.

A major factor in selecting Isidis as the landing site is that it is low lying (to give the parachutes chance to work), and slightly north of the equator (to take advantage of the relatively warm spring nights and thus minimise the thermal stress on Beagle 2's electronics).

So far as can be deduced prior to landing, the surface within the landing ellipse is hardened dust with about 15% of the area covered by rock fragments, mostly smaller than house bricks in size. The most detailed images available from previous Mars orbiter missions show details as small as a couple of metres across. These reveal a few ridges and numerous cones occupying about 10% of the total area and each a few hundred metres across that may have been produced by small explosive volcanic eruptions. If so, they indicate the presence of ice in the local subsoil, making Isidis Planitia an appealling place to search for signs of life.

So what will the view from the lander reveal? Most likely a stone-strewn plain. There is only a one in ten chance of landing on a volcanic cone, and perhaps a one in five chance of a nearby cone being visible from the lander. There is an even smaller chance of landing among substantial sand dunes, though small wind-blown drifts of dust are perhaps more likely. The camera's vantage point on a relatively short robotic arm may not be great for distant views, but we expect to get fascinating close-ups of individual rock and soil specimens prior to studying them with Beagle 2's considerable array of analytical devices.

Isidis is a very good projected landing site; it is also being considered as the location for one of the NASA Athena rovers which are also landing in gas-filled bags and subject to the same engineering constraints as Beagle 2.