Interesting recent observations have been made by various space probes. Some that I find interesting from the past few weeks are from Stardust, Opportunity and Spitzer Space Telescope. These are somewhat related in that they deal with impacts and planetary evolution.
Over about the last 70 years we've learned an incredible amount about the formation of planets. There are theories about how the planets condense from the stuff surrounding their mother stars, about how they form, age, and die. Without ways to test the theories or evidence that mechanisms from the theories have actually occurred, the theories aren't much more than words.