Interesting concept this. What would Martian anthropologists make of us Earth-dwellers if all they had to go on were examples of contemporary art? The Barbican Art Gallery, disguised as a museum on the red planet, plays out this indulgence in a new exhibition.

Those crafty aliens have bagged some prize exhibits. Warhol, Hepworth, Hirst - and a Henry Moore maquette, covered in molluscs for some reason. Dozens of cultural relics are scattered around in loosely connected groupings, such as 'ceremonial objects', 'icons' and 'ancestor worship'. The latter, for example, houses modern works that pay homage to earlier artists, such as a golden replica of Duchamp's urinal.

Make sure you pick up a free audio guide. Most of the humour and insight lie in the commentary, which borrows heavily from Douglas Adams. There are wry touches here - the Barbara Hepworth abstract that 'resembles an inhabitant of Cassiopaea Delta', and the notion that C3PO is a well-known celebrity in the wider cosmos, whose misadventures are woefully distorted in the Star Wars 'documentaries'. But these flashes of humour are sporadic, and the commentary covers only a handful of exhibits.

It's not a bad collection; perhaps a quarter of the curios will make you think and question. But there's too much guff and the interplanetary theme fails to hang together. They could have made more of Damien Hirst's spot pattern, for example, which functioned as a calibration target on the ill-fated Beagle 2 probe. This real instance of sending modern art to Mars is tucked away in the upper gallery.

Diverting but patchy. Still, we for one welcome our Martian overlords.

Martian Museum of Terrestrial Art runs till 18 May and costs eight of your Earth pounds.