Ultima Thule has a new photo for a glass
The closest image of the ancient object of Cape Belt, captured by the spacecraft New Horizons, flew until January 1, shows a relatively smooth face uninhabited by the impact craters.
"This thing is simply not covered with craters," says planetary scientist Kelsey Singer of the Southwest Research Institute in Boulder, Colorado, in a photo published on January 24th.
This lack of impact marks suggests that Kaiper's Belt, a reservoir of ancient cosmic rocks outside Neptune's orbit, has fewer objects than scientists expected. If true, it could mean that the planets' predecessors grew up quickly without leaving many protruding crumbs behind.
Images taken when New Horizons flew past Pluto and its moons in 201
"If you can not get geology to erase Haron's craters, in particular, it's a sort of inescapable conclusion that you just do not have to make craters first," says Singer.
The real test of this idea came with Flyby on Ultima Thule, whose official name is MU69. If MU69 did not have small craters, which would mean that there are relatively few small objects in the outer solar system to collide with them, Singer and colleagues argue in an article published at arXiv.org in December.
The last photo of MU69 shows only a few small craters on its top edge – where the shadows make craters craters in the relief – probably left from objects about 100 meters wide. A large depression of the smaller of the two shovels of the object may be a crater hit by a subject about 700 meters wide.
A shortage of small objects that could penetrate bodies like MU69 may exclude some theories about how planets and their ancestors. One of the ideas for this time in the early solar system is that the powder grains slowly combine to build gradually larger bodies. Another theory suggests that larger objects collide and break with each other for strikes. But the two scenarios are likely to have left very small objects floating around Kaiper's belt today, Singer says.
If the protoplanets harden directly from the nebula of gas and dust that preceded the formation of the solar system, they could have developed up to tens and hundreds of miles wide relatively quickly, Singer says. This means that there will be a few small cosmic granules and bits.
Planetary scientist Alessandro Morbidelli of the Cote d'Azur Observatory in Nice, France, says it is premature to draw conclusions. The crater counts on Pluto and Charon is not reliable, he says. While he agrees that MU69 is the "ultimate test," he says higher resolution shots are needed to see if the barely noticeable face is kept under close scrutiny. The current best image was made seven minutes before New Horizons' closest approach to MU69 when the spacecraft was still 6,700 kilometers. Better images are on the computer of the spacecraft waiting to be transmitted to Earth.
New Horizons will continue sending back MU69 data until September 2020