Mysterious, nearly invisible objects known as “darkness”. cometsIt may pose a bigger threat to Earth than scientists thought, a new study suggests.
These small, rapidly rotating objects wander near Earth, likely after migrating from the far reaches of the solar system. They can be a source of water and other volatile elements – and also a potent source of danger.
Usually, comets are very distinct from ASTEROIDS. Comets come from the outermost region of the solar system, where temperatures are low enough to allow molecules like water to freeze. While comets usually have stable orbits, they can occasionally be disturbed by gravitational interactions with giant planets, sending some of the icy rocks spiraling inward. solar system. When they do, heat from the sun causes them to break apart—a process that also gives comets their signature tails.
Asteroids, on the other hand, usually live in the inner solar system, usually between Mars and Jupiter. They are much more rocky than their cometary cousins and, therefore, can survive much longer in the sun’s glare. But even they occasionally fall into unstable orbits that bring them dangerously close to Earth.
But there’s a strange third type of space rock that astronomers have only recently begun to identify: dark comets, which behave like both asteroids and comets. Now, in a paper accepted for publication in the journal Icarus, a team of astronomers has attempted to identify the mysterious origins of dark comets.
Dark comets are small – only tens of kilometers across. They show no visible outgassing or evaporation of volatile elements such as water. But they don’t move in perfect orbits either. Instead, they show evidence for “non-gravitational” acceleration, implying that there are some other forces capable of gently nudging their orbits.
All small objects in the solar system, including asteroids, have some non-gravitational acceleration, but astronomers can usually identify the cause. For example, asteroids are unevenly heated by the sun, which causes a small but measurable shift in their orbits.
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The researchers found that the non-gravitational acceleration of dark comets is not consistent with uneven heating, so there must be another source of acceleration. The team thinks that dark comets are indeed out of gas, which could cause their own non-gravitational acceleration, just to an undetectable level.
Dark comets also spin very quickly, which means they must have enough internal strength to keep from breaking apart. From this, the researchers concluded that dark comets have a similar composition to asteroids and are probably the result of the fragmentation of a larger object.
Based on these lines of evidence, researchers suspect that dark comets likely originate in the main asteroid belt between Mars and Jupiter and are perturbed from their orbits through gravitational interactions with Saturn. So dark comets may be asteroids, but with a strange flavor—they’re asteroids loaded with an unusually large amount of light molecules, like water, that can evaporate when the objects enter the inner solar system. Therefore, the researchers suggest that dark comets may be a possible candidate for how early Earth received its water.
Meanwhile, the unstable orbits of dark comets and their unlikely combination of properties make them particularly dangerous near-Earth objects. They are small, fast and difficult to detect. More importantly, they don’t behave the way their more familiar asteroid and comet cousins do, making them unpredictable, the researchers found.
To help you protect the Earth from potential threatswe will need to study rogue populations such as dark comets in more detail to better detect them and predict their future motions.