Large craters cover more of the moon’s surface on its nearside than its farside, according to new maps from NASA’s GRAIL spacecrafts.
Scientists haven’t always agreed on the size of lunar craters because lava filled many of the biggest impact basins on the side of the moon that faces Earth. For nine months in 2012, astronomers used GRAIL to map the thickness of the crust in and around the craters. Based on the data and simulations of lunar impacts, the hotter nearside of the moon would have formed craters with up to twice the diameter compared with similar impacts on the cooler farside.
The GRAIL data also suggest that astronomers should not use measurements of the basins on the nearside of the moon to draw conclusions about the rate at which craters struck the planets of the inner solar system 4 billion years ago, the researchers report November 8 in Science.