 "NASA finds seven new dark comets that might have brought life to Earth")
The National Aeronautics and Space Administration (Nasa) has announced the discovery of seven new 'dark comets' taking the total number to 14. The dark comets are a newly defined type of near-Earth objects, somewhere between an asteroid and a comet.
Planetary scientists define them as comets and asteroids whose orbits of the sun bring them close to Earth, resembling asteroids but can speed up unexpectedly, which suggests that they may be firing jets of gas just like comets.
The National Academy of Sciences published a recent finding revealing the intriguing differences among these objects.
New comets detected in two distinct populations
The scientists have reported the detection of these seven dark comets in two distinct populations. They assert that larger dark comets reside in the outer solar system while the smaller dark comets in the inner solar system.
The lead author and a postdoctoral fellow in the Department of Physics at Michigan State University, East Lansing, Darryl Seligman said, “We had a big enough number of dark comets that we could begin asking if there was anything that would differentiate them.”
“By analyzing the reflectivity,” or albedo, “and the orbits, we found that our solar system contains two different types of dark comets,” he added.
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The dark comets may have delivered materials which are necessary for the development of life on earth, the authors suggest. This was also suggested by a paper published in July in Icarus, which argues that dark comets are much more common than previously thought and may have delivered water to the earth a long time ago.
Between 0.5 and 60% of all near-Earth objects could be dark comets from the asteroid belt between Mars and Jupiter, the scientists say. Dark comets also contain ice just like comets do but not asteroids.
Asteroid that wanted to be a Comet
The first dark comet was found in 2016 while scientists were observing the orbit of asteroid 2003 RM, which appeared to move slightly from its orbit in a way thought only possible by comets propelled by jets of gas.
The co-author from NASA’s Jet Propulsion Laboratory, California, Davide Farnocchia, said, “When you see that kind of perturbation on a celestial object, it usually means it’s a comet, with volatile material outgassing from its surface, giving it a little thrust.”
“But try as we might, we couldn’t find any signs of a comet’s tail. It looked like any other asteroid — just a pinpoint of light. So, for a short while, we had this one weird celestial object that we couldn’t fully figure out,” he added.
Dark Comets: Potential source of water and life
How and when dark comets delivered water to earth is going to be difficult to prove. The main asteroid belt is very likely to be the source of near-Earth objects. Such objects remain in their current orbits only for around 10 million years. The solar system is around 4.5 billion years old.
Seligman said, “Dark comets are a new potential source for having delivered the materials to Earth that were necessary for the development of life. The more we can learn about them, the better we can understand their role in our planet’s origin.”