I was wondering if we have ways of measuring the age of planets. If so, do we know which planets are oldest and which are youngest?
The ages of igneous rocks can be determined from the decay of radioactive elements. If we have a sample, we can estimate the age of the planet. Thus we know the Earth, Moon, Mars, and the asteroid Vesta each formed between 4.5 and 4.6 billion years ago. We do not have identified samples of other planets for this sort of dating, but the theories of solar formation tell us to expect that ll the planets in the solar system are essentially the same age.
NLSI Interim Director
October 2, 2006