This depends on the laws of your country.

In Canada, they belong to the owner of the property they land on.

So if it lands in your yard you own it, if it lands on "Crown land" the government owns it.

Looks like things are a bit different in the US where the "Bureau of Land Management" allows private citizens to claim up to 10 lbs of material for free, and has a fee structure for people who collect for profit?

Your point of "jealousy" is unclear. why would a scientist who wants to study them be jealous?