Of the 24,000+ meteorites collected on Earth, only 30+ have been identified as meteorites from Mars. They are generally divided into three groups (all with relatively young ages slightly over 1 billion years old). The groups are the Shergottites, Nakhlites, and Chassignites. A Martian meteorite that does not fall into one of these groups is ALH 84001, a cumulate rock composed mostly of orthopyroxene, which is much older than all the others with an age of 4. 5 billion years. A NASA-sponsored research team reported in 1996 that ALH 84001 may contain evidence of past primitive life on Mars--an idea that remains a topic of great debate and continued investigation. (See Mars Meteorites compiled by Ron Baalke from the Jet Propulsion Laboratory. )