Life on Mars?

Glossary

archaea. Single-celled organisms similar to bacteria as they do not have their genetic material enclosed within a nucleus. Archaea are prokaryotic but genetically similar to eukaryotes so are placed in a separate kingdom 'the archaea'.

asteroid. A small Solar System body that orbits the sun. Most asteroids are thought to be the result of debris left over from the formation of the solar system and occur in the region between Mars and Jupiter. Collisions among the bodies in the asteroid belt and adjacent planets displace fragments and place them on a collision course with Earth. The asteroid belt is thought to be the source of most meteorites.

electromagnetic radiation. Energy that travels through space in the form of waves. The highest frequencies are gamma-rays; the lowest frequencies are radio waves (microwaves are a type of radio wave). All electromagnetic radiation travels at light speed – 300 000 kilometres per second in a vacuum. Shorter wavelength radiation (eg, ultraviolet) carries more energy and is likely to be more harmful to living tissue.

electron microscope. An instrument that uses electrons, instead of light, to produce a magnified image of an object. The magnification that can be achieved is about one thousand times that of a light microscope.

eukaryotic. Describes those cells that have their genetic material (chromosomes) contained within a nucleus.

meteorite. A fragment of an asteroid or a planet that has been broken off by a collision and eventually falls on the Earth. It consists of solid matter which survives the descent and lands on the Earth's surface.

polycyclic aromatic hydrocarbon (PAH). An organic compound containing only hydrogen and carbon. The atoms are organised into a number of stable, unsaturated ring structures, like benzene. The main sources of PAHs on Earth are vehicle exhaust and smoke from burning fossil fuels.

prokaryotic. Describes those cells, or organisms, that do not have their genetic material enclosed within a nucleus. Bacteria and archaea are prokaryotic.

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Posted November 2008.