400 million years to build a planet?

[stevebowers]

Like you said, the entire moving group is also of a similar age: 400-500ish million years old. On the other hand, it does have foreign stars crossing through it. A rock from a X-billion year old planet would give me a jump start, at least allowing well-evolved algae to take root earlier.

This possibility merits further consideration. A typical young cluster is anything from less than one to ten light years across, and might exist in a closely bound state for up to a hundred million years; in that time and with that cross-section it is likely to intercept a small number of older stars, which will take a few thousand years to pass through. So the possibility of cross-infection is non-zero.

For some reason a few clusters never disperse, such as Messier 67;
https://en.wikipedia.org/wiki/Messier_67
this ancient cluster will have had numerous close encounters, and it is not impossible that the entire cluster is infected with life- perhaps of several different kinds.