Recent content by okiedokie

atmosphere. If the gravity o? Mercury and Mars both have almost the same surface gravity, but only Mars has an atmosphere. If the gravity of Mars is enough to hold a significant atmosphere (although just barely), why can’t Mercury hold an atmosphere too?

...neighboring star and photograph its p? Suppose that, in some future century, we manage to send a probe out to a neighboring star and photograph its planets up close. We discover three terrestrial planets orbiting this star, with surfaces that are as described below. What can you conclude...