4.5 billion years ago, a Mars-sized body was believed to have impacted a young Earth, and this planetesimal’s obliterated remains coalesced into what is now our Moon. However, certain striking similarities between the Earth and Moon question the likelihood of this event. Two recent papers investigated the giant impact scenario, only to come to opposite conclusions. Read on to hear more about this lunar enigma.
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.