While other astronomers are scanning deep space for signs of the existence of the mythically theoretical Planet Nine, a group of researchers in Colorado has been looking down instead of up and found evidence in a meteorite of what may have been a small planet in the early days of our solar system. Is it still around? Can it help find Planet Nine? If it’s designated a planet, will Pluto be upset?
“Carbonaceous chondrite meteorites record the earliest stages of Solar System geological activities and provide insight into their parent bodies’ histories.”
According to a new study published in the journal Nature Astronomy, carbonaceous chondrite meteorites are like a diary, history book or crystal ball into the celestial bodies they once were. Chondrites are stony, non-metallic chunks that have never been changed by heat, cold or other outside forces, so they are identical to the larger rock they came from. Only a small percentage of them (4.6%) are carbonaceous – containing high percentages (3% to 22%) of water, silicates, oxides, sulfides, and the minerals olivine and serpentine. The uniqueness of the combinations tells researcher like Dr. Vicky Hamilton, Southwest Research Institute (SwRI) Staff Scientist and first author of the study, the identity of the parent and much about its own characteristics.
While most of the asteroids that are remnants of the formation of the solar system are in orbit between Jupiter and Mars, a few break away and collide with Earth. Such an event happened in 2008 when a 9-ton, 13-foot diameter asteroid named Almahata Sitta (AhS) exploded into about 600 meteorites that crashed into Sudan – exactly where scientists had predicted, which allowed them to recover 23 pounds of pieces and fragments. Hamilton and her team were given a 50-milligram (.0017 ounce) shard to analyze. Believe it or not, according to the press release, that was enough.
“Spectral analysis identified a range of hydrated minerals, in particular amphibole, which points to intermediate temperatures and pressures and a prolonged period of aqueous alteration on a parent asteroid at least 400, and up to 1,100, miles in diameter.”
Amphibole, a silicate mineral that forms needlelike crystals, has only been found in one other meteorite – the Allende which exploded over Chihuahua in 1969 and is the largest carbonaceous chondrite ever located. Over 2 tons of material was recovered and it has become the most studied meteorite of all time. Almahata Sitta is not Allende, and its estimated maximum diameter shows it wasn’t Pluto either (Pluto’s diameter is 1,476.8 miles). However, it would have been twice as big as Ceres (587.8 miles), the largest object in the asteroid belt, so it was definitely a dwarf planet. Are they sure it no longer exists? Could it be out of sight in a Planet Nine-type orbit?
“Hamilton explains that the body that the meteorite came from will no longer exist, at least not in large form, but the evidence the meteorite provides could change our understanding of the materials that asteroids contributed towards the formation of the Earth and other planets.”
Oh well. On the positive side, the samples from asteroids Ryugu and Bennu brought back by Japan’s Hayabusa2 and in 2023 by NASA’s OSIRIS-Rex will be compared to those that have crashed to Earth, giving the researchers more insight on what their parents looked like and how much, if any, change Almahata Sitta and Allende went through as they passed thought the Earth’s atmosphere.
It all adds up to a growing picture of the early days of our solar system coming from mere shards of what were once dwarf planets … and maybe larger ones. While we shouldn’t give up on Planet 9, Planet 8 ½ is real and here.