We've already reported on an exceptionally beautiful pallasite meteorite which will be providing excitement in Bonhams' Natural History auction next week.

However, other meteorite collectors may be more excited to see a couple of very special spacerocks from other worlds on offer. Material known to have originated on other heavenly bodies is extremely rare and coveted.

Firstly, there is an NWA 3163 Lunar Slice. Found in August 2005, the exterior is almost completely coated by a thin, transparent, greenish fusion crust.

The pale gray interior has multiple shock fractures (with very minor calcite coatings) and some thin glass veins. The specimen also has a very good, textured fusion crust. Most lunar meteorites are kept in the collections of museums and institutions, making this large specimen a rare find in the private marketplace.

Only just over 15 kilograms of lunar meteorite have been discovered so far in total. At a weight of 25.5g, this slice is expected to fetch $30,000 - 40,000.

Lower in the listings, but at least as interesting, is a complete specimen of NWA 998 - a Martian meteorite.

The chances of anything coming from Mars...  the NWA 998 meteorite

Like the Murchison meteorite, NWA 998 has a further claim to fame: scientific importance. Whilst all known meteorites are the object of study by someone somewhere, this meteorite is a confirmed meteorite from Mars which is thought to contain water-bearing minerals, hence strengthening the case for the view that Mars had liquid water on it at some stage.

Other meteorites might show wear from water damage, but the NWA 998 is the first to be found showing these characteristics, and in fact the rarity of samples available is increased by the fact that most of the meteorite has been retained for study and will not be passing into private hands. Naturally that also helps to make it an excellent investment.

The 5.04g piece is expected to sell for $10,000 - 12,000 in Bonhams' sale which takes place in New York on May 17.