Today (June 30th) is asteroid day. For this auspicious (yet anxious-making) holiday, I have been saving two asteroid-related miniature stories ripped from the headlines.
First, we return to the dwarf planet Ceres, the largest object in the asteroid belt. We need to revisit the bright spots upon the dwarf planet’s surface. Ever since the New Horizons spacecraft began to approach the little world, these glistening spots have fascinated the astronomy community. Initially scientists thought that the spots were composed of hydrated magnesium sulfate (a substance quite similar to the Epsom salts sold for bathing and foot-soaking), however it now seems like the shiny patches are made of something else entirely. According to astronomers, the particular chemical in these glistening patches actually turns out to be sodium carbonate–a salt formed from carbon. On Earth, this chemical usually forms in evaporitic conditions–when water evaporates from a lake, sea, or hot springs. This seems to indicate that the geology of Ceres is more complicated than initially thought—instead of a big ice crystal which has always been the same, the miniature planet has undergone changes: surface water evaporated to leave these mysterious chemical deposits. Hopefully finding out about Ceres’ past can teach us more about how planets form (or don’t form).
Second, we turn our eyes back closer to Earth to take in the newly discovered “second moon” a tiny asteroid about the size of the great pyramid of Giza which seems to be orbiting Earth. This new asteroid, called 2016 HO3, is not really a true moon but a quasi-satellite: it sometimes loops around our planet because Earth and the little rock both orbit the sun on a similar circuit. The asteroid orbits the sun in 365.93 days (just slightly longer than Earth’s orbit of 365.24 days). Thus, for the next few hundred years it will act like a true moon as our orbits converge. The rock is about 40 meters (130 feet) across by 100 meters (328 feet) wide. It is a bit strange to think about it up there hidden in the darkness, but it is a fairly comforting asteroid day story. 2016 HO3 is never destined to hit Earth. The really bad asteroids seem to be the ones we don’t know about (so it is time to keep our eyes on the skies and learn more).