Hold on to Your Moons! Ice, Atmospheres and the Grand Tack

Hold on to Your Moons! Ice, Atmospheres and the Grand Tack

Among the many ideas proposed to explain the formation of our Solar system, one of the leading theories is the “Grand Tack”. This scenario suggests that, early in their formation, Jupiter and Saturn undertook a sweeping voyage, migrating from the outer Solar System to within the orbit of Mars. The two huge planets then entered an orbital resonance with each other, before their cosmic dance took them back out to their current positions. The model neatly explains, amongst other things, the current locations of Mars, the Asteroid Belt and the outer planets—which are hard to recreate in models assuming a more static Solar System.

Mugged by a Passing Star

Mugged by a Passing Star

A close encounter with another star can disrupt the protoplanetary disk of a young star, leaving a smaller disk behind. Can we learn anything about the encounter from the size of the remaining disk? Read on to find out!

Forming Mercury and Iron-rich Exoplanets

Forming Mercury and Iron-rich Exoplanets

Mercury’s high density has been a longstanding puzzle in planetary science. Its density means that it must have a significantly higher iron abundance than Venus, Earth, Mars, or the asteroids, probably in the form of a large iron core. NASA’s MESSENGER mission has challenged many of the hypothesized ways to create an iron-rich Mercury; a new hypothesis is required.