Weird Issues: Are comets asteroids or are asteroids comets?

Astronomy Cast


Used to be so simple. Comets were snowballs from the outer solar system and asteroids rocks walks from the inner solar system. But now everything's all shades of gray. STRANA found asteroids have behavioral comets and college the behave like Asteroids Pamela. Make sense of this for him. It's a continuum of objects that simply want to mock with our desire to name mm-hmm everything let's face it. Human beings like to put things in boxes and and this is a problem for us when it comes to the solar system because we used to think it was so easy we had trust real world. We had gas giants we we had asteroids. We had icy things and and it's all falling apart as we've discovered that well somewhere between the icy things in the asteroid. Things is a continual. And there's there's no discrete gap or anything no set the technical term icy things and asteroid things. Technically it's comet or send tour or Kuyper belt object depending on where they are and then of course the cloud. We need to stop naming things based on where they're located located right or just like trying to classify them don't judge just that's just gonNA drive yourself crazy so and then they're gonNA set off a debate on the Internet where people are going to yell at each other about whether poodles planet or not. And we're still going to have to hear about it now however the classic we're just GonNa go with Planet Classic Play Planet Classic. Okay all right so so then back. In the olden days of your What was an asteroid? It was a dry rocky. Object like killed the dinosaurs awards and exists in the asteroid belt. That in general is made of metals of carbons of silicates and and is dry. That was wrapped is where we started. Asteroids that you've got the the ones that are near the earth we've got the ones as you said in the main asteroid belt and then we've got the trojans interesting side note. Did you know that. There is roughly in the same order of magnitude as many objects in Jupiter's Trojan Asteroid Area as in the main asteroid. Bill Lloyd didn't that's is you know that either the I know until I was doing an episode about it in other the words the solar system has second asteroid belt. And you didn't even know about it. I mean we all knew the trojans were there but we didn't know that they work and they're not even third third. They're really just to clouds that Leonie Trail Jupiter like like yeah parade on procession around our solar I system and yet there is as many objects roughly as in the main asteroid belt. So anyway interesting thing I just discovered So okay so so. Asteroid Rock Metal Draw S.. What's a comet? Eight comment is a Blob of mostly Isis. So so here you have. Water is nitrogen ice dry ice isis. Things that can be liquids. It's Things that will become gassy tails and we knew that mixed in with that was some gravelly bets but it was considered to be mostly Salihi ice and cold Gucci does a great of she does a great science show where she will make a comment with yes and and and this is something that that astronomers have been doing for ages because you can get all of the ingredients to make a comment in a bowl pretty much. It's from your local grocery store. If your local grocery store happens to have dry ice and I it's just a little bit of Corn Syrup a little bit of molasses lassus dry some water some ammonia and then you grab a handful of dirt from the art right and that's a comet and so it's pretty pretty clear right like obviously one is a chunk of rock and metal rock or metal rock and metal rock or metal at the other is a chunk of water with maybe a little bit of dirt thrown in meet both in volatile ICES. When did this categorization and start to go off the rails? What some discoveries that were made that made this clearly problematic? Well one one of the problems was simply the story we had told ourselves about. Our solar system turned out to be wrong and one of the stories that we told ourselves about our solar system. was that all of the water. We have all all of the earth's oceans came to us through the bombardment of comets on the surface of our world but when we started looking at the composition position accommodates the waters that comets are made of. Don't match the water that we have here on earth so there is a sudden w T.F. If water what's wrong with you and a realization that all the water we've got had to come from somewhere else now. It didn't end there it. It never ends that simply said but but just like just before you move on so we know Oh that like based on whatever the deterioration the tritium is the ratios of of what are the kinds of hydrogen involve are involved in making water ready the ratio Samyong comments right and so. Have you sample the water in the earth's oceans and then you look at the samples that had been done in in looking at comet. They don't match perfectly. I mean obviously they both have water in them. But but it's like the initial recipe doesn't seem to match so it's to the comments couldn't have been the source of all of an and in fact having looked at multiple comets. It's if our water came from the as we so far seeing them typical comments. It still doesn't work so it it. It can't even be like the smallest fraction of our water. Came from comments So yeah it's not comments. Okay so the so then. We have a clue but that doesn't mean anything right just means that the water came from somewhere else. Maybe it was formed in place as the earth formed and then maybe it was a part of underground and in welled up over time as the Earth Glenham models. That's out there. But that's no longer the dominant model because we have another Attacker that has been identified. It's it's been realized that asteroids have water in fact they appear to have a lot of water and big astros like series may even have subsurface sees of water right so within how was how were these discoveries made well. It's it's been a whole combination of looking at nearer by asteroid looking things and realizing shoot. These are actually active. They actually periodically spray material outwards and thinking. Well some of them were just going to call. I'm dead comments. We're going to refer to these objects that clearly used to be comets. Their orbits change they got crusted over with stuff will blame them on being former comets comets and about works to a point but then we started doing things like sending probes out to visit asteroids and when we got to series. We saw cry of alcoholism going on there are massive features on series that appeared to be former role. Kano's that have now begun to slump and there's at least one. What appears to be still active volcano in place in the bottom of a crater and these this is salty stuff that's getting sprayed up and then settling down and crusting over the volcano that that it is

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