Unraveling the Mystery: What Causes Pebbles to Break Down After Leaving Comets?
A group of 45 researchers from around the world, led by Dr. Peter Jenniskens, an expert in studying meteors at the SETI Institute, has shed new light on how comet dust breaks down in space. Their findings challenge the old idea that fast collisions smash comet debris into tiny bits.
Their research, published in the journal Icarus, points to heat as the main culprit behind the demise of comet dust.
Dr. Jenniskens, who heads up a global network called “CAMS” sponsored by NASA to watch for meteors using low-light video cameras, explains, “Comets shoot out most of their debris as small particles ranging from sand grains to pebbles, which form streams of meteoroids that we see as shooting stars during meteor showers. On the other hand, the zodiacal cloud consists mostly of particles as tiny as tobacco smoke, which are hard to detect even with radars.”
To understand more, the team looked at the ages of meteor showers by studying how spread out their debris is. Then, they checked how quickly the larger meteoroids disappeared compared to the smaller ones.
Next, they examined how close these streams got to the Sun. If collisions were the main cause, the pebbles would break down faster the closer they were to the Sun.
Dr. Jenniskens elaborates, “Considering there’s more comet dust nearer to the Sun, we thought collisions there would break down the pebbles even faster. But surprisingly, we found the pebbles held up better than we expected.”
Their conclusion? The destruction of these pebble-sized particles depends on the highest temperatures they encounter along their orbit. The study suggests that it’s thermal stress, not collisions, that cracks the larger meteoroids near Earth, all the way to the orbit of Mercury. As they get closer to Mercury’s orbit, these particles break apart due to significant material loss.
In a nutshell, it’s not about high-speed collisions smashing comet debris, but rather the heat they encounter along their journey in space.
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