The Kuiper Belt lies in the dimly lit spaces of our solar system beyond Neptune's orbit. This is a region about 35 to 50 times farther from the Sun than Earth, populated by icy bodies so sparsely dispersed that they never had the chance to collide and cluster into objects of planetary size.
Pluto is the biggest we know, but only fair. In the last two decades, telescope surveys found that several thousand more were only a few tens of kilometers away in size.
The problem is that most objects of this size are too small to be discovered by telescopes. So it will be hard to figure out how many small but invisible bodies are actually in the Kuiper Belt. Now, a new work published in Science has used a sophisticated method to find out.
This is important because scientists believe that objects of the Kuiper belt survivors since the formation of a solar system are primeval cloud of dust and gas. This means that their size distribution could tell a great deal about how the material from which the planets grew was originally assembled.
Instead of counting the small objects of the Kuiper belt directly, researchers stand behind the new study that counted the craters that were made by the sample of objects that cover the surfaces of Pluto and its largest moon, Charon, have influenced. There, craters with a diameter of 1
This is already well below the telescopic detection limit for Kuiper belt objects themselves, but images from the flyby of NASA's New Horizons mission in 2015 allow the mapping of craters up to 1.4 kilometers.
These must have been made impacts of objects of the Kuiper belt, which are not much larger than 100 meters.
Researchers' analysis shows that for craters as small as 13 km, the frequency of impacts is different for both Pluto and Charon seems to agree with what is expected from the known size distribution for objects of the Kuiper Belt.
However, with smaller craters, the abundance falls dramatically, and thus the abundance of Kuiper belt objects must be able to produce these craters.
The same is not true for the well-documented asteroids that collide with the bodies in the region of Jupiter, Mars, and Earth, nor is it compatible with theoretical models.
The interpretation of the most cratered terrain led the researchers to rule out that the small craters were erased in the last four billion years by geological regeneration such as cryovulcan activity (eruptions of iced fluids).
This confirms the conclusion that smaller craters occur were never made in the expected number, so there must be a mysterious Kuiper belt object deficit less than one-and-a-half kilometers in size.
Blorping and Flomping
When the researchers, led by Kelsi Singer of the Southwest Research Institute in Boulder, Colorado, did their work, no one had seen in detail a small object of the Kuiper Belt.
New Horizons He recently flew past a 30-kilometer-long 2014 MU₆₉ (more controversially nicknamed "Ultima Thule") on January 1, and has now probably broadcast the best images we've received.
Sometimes referred to as "snowman-shaped". It is a two-lobed "contact binary system" that was almost certainly formed by a fusion of two round objects that went so slowly and gently that none of the components was deformed.
But what happened before? In particular, looking at the larger of the two lobes, one can see the appearance of traces of constituents that join together so violently that they join together to form an approximate sphere, but with insufficient force to destroy each other.
These ideas have led to strange new terms. "Blorping" refers to the collision-related gathering of material to assemble each of the flaps, and "flomping" describes the coincidence when two flaps collide without causing deformation.
More importantly, this could give an insight into the processes that were robbed of the Kuiper Belt of smaller objects that would otherwise have made small craters on Pluto and Charon.
The relative lack of small Kuiper-Belt objects may be due to the fact that they do not collide but blur together – eventually becoming objects like 2014 MU₆₉.
If this is correct, then when you try to count them, we see a record of growth instead of collision splitting.
The speed of the orbit is slower the farther you are from the sun. Therefore, we would expect collisions in the Kuiper belt to be less violent than in the inner solar system.
But even if a "blorp" event involving two lumps instead of shattering them, it is likely that the ice will be the bulk of their substance much less brittle and muddy than we expected.
This is crucial information, since these lumps are made from the raw material that made up the Solar System and throw important light on its development.
David Rothery, Professor of Planetary Geosciences, The Open University. 19459 005]
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