Some information missing

1. How can anyone know with certainty that any of the meteorites really are Martian in origin? 2. It says there have been 24,000 meteorites - When? What time frame are we talking about? Who is counting, and how could anyone know how many meteorites have hit the Earth in any time frame? Is this just an estimate, and if so, by who?

Thanks for catching this. An edit has been submitted, reviewed, and published to clarify. The 24,000 are known meteorites (the word the source uses is "discovered").