Earth's Moon Reveals An Ancient Secret. Many astronomers think that during an ancient era, termed the Late Heavy Bombardment, our young Moon was violently battered by a marauding multitude of invading asteroids that crashed onto its newly formed surface. This attack of pelting objects from space occurred about 4 billion years ago, and the shower of crashing asteroids excavated impact craters, and also slashed open deep fissures, in the lunar crust. This sustained shower of merciless impacts increased lunar porosity, and opened up an intertwining network of large seams under the Moon's surface.
The tiny moon--which for now has been designated S/2015 (136472) 1, and playfully nicknamed MK 2, for short--is more than 1,300 times dimmer than Makemake itself. MK 2 was first spotted when it was about 13,000 miles from its dwarf planet parent, and its diameter is estimated to be about 100 miles across. Makemake is 870 miles wide, and the dwarf planet, which was discovered over a decade ago, is named for the creation deity of the Rapa Nui people of Easter Island.
Earlier infrared data did not have sufficient resolution to separate MK 2 from Makemake's veiling glare. The astronomers' reanalysis, however, based on the more recent HST observations, indicates that much of the warmer surface spotted earlier in infrared light may simply be the dark surface of the companion MK 2.