By Paul Rincon
BBC News Online science staff in Paris, France
A new space mission concept unveiled at a Paris conference aims to look inside asteroids to reveal how they are made.
Studies of asteroids would aid Earth-protection strategies
Deep Interior would use radar to probe the origin and evolution of two near-Earth objects less than 1km across.
The mission, which could launch some time later this decade, would also give clues to how the planets evolved.
The perceived threat of asteroids colliding with our planet has renewed interest in space missions to understand these mysterious bodies.
Deep Interior would use two 30m-long radar antennas to build up a picture of the structure of the asteroids, including compositional boundaries and faults, and its topography.
This should show whether the asteroids are solid all the way through or are essentially floating piles of rubble.
It is intended to rendezvous with two asteroids which are each under 1km in size: Nyx and 1999 ND43.
Nyx is a so-called V-type asteroid, containing stony irons, chondrites and pyroxene. The other target, 1999 ND43, is not well understood.
The asteroids have partially been chosen because they are easy to reach.
The probe would also carry a radio tomography instrument - to examine electromagnetic properties - and two colour cameras.
A proposal for the project, described here at the Committee on Space Research (Cospar) scientific assembly, was submitted to Nasa two weeks ago.
The scientists behind the concept hope that, if accepted, the probe could launch as early as 2009.
An asteroid mission concept - called Don Quijote was recently given priority over five other potential asteroid projects by the European Space Agency.
The European mission would impact an asteroid
The mission is designed to help scientists understand how an asteroid on a collision course with Earth might be destroyed or deflected.
This mission would involve two spacecraft - Sancho and Hidalgo - launched on different trajectories to the same asteroid. Sancho would arrive first and orbit from a safe distance.
It would then measure the effects as Hidalgo is sent crashing into the asteroid's surface.
Nasa has a similar mission - Deep Impact - which will blow a hole in the comet Tempel 1 and measure the effects.