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SciShow explores two celestial mysteries: the origins of a meteorite that crashed into a house in California, and who’s releasing chemicals into the atmosphere that were banned more than 25 years ago?

Hosted by: Reid Reimers
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Two years ago, Lisa Webber was asleep in her bed in Novato, California when she heard a bump in the night. Turns out, it was a meteorite hitting her roof. And last week, astronomers said they finally pieced together the details of that rock's astonishing journey, billions of years in the making.

It seems the story began not far from where it ended, on earth. Six other fragments of the same meteor were found in the area and its fiery descent into the atmosphere was captured by NASA's CAMS program which scans the sky for meteors and lets astronomers predict where the debris might land. Using all this data, an international team of astronomers were able to calculate the trajectory of the Novato meteorite. And they traced it all the way to the intermediate region of the asteroid belt between Mars and Jupiter.

The specimen that smacked into Lisa Webber's garage that night turned out to be strongly magnetic and rich in olivine, the same material that surprised astronomers last week when it turned up in intergalactic dust from outside our solar system.

This composition indicated that the Novato meteorite came from a rock called an L chondrite, and the poor guy seems to have had a pretty unstable life, pinging around the whole inner solar system, and experiencing more than one collision along the way.

To figure out all that this meteorite has been through, the researchers used radiometric dating. This can help establish the age of a celestial object by measuring the amount of radioactive isotopes it has. Because some events, like massive impacts, can create isotopes, ionizing elements within the rock with their immense pressure, friction and heat. And because we know at what rate these isotopes decay into other elements, the amount that's left can help us figure out how old this sample is and what's happened to it along the way.

Using this technique, researchers found evidence in the Novato rock of a big impact, about 470 million years ago, an indicator that's common in other L chondrites. But they also found traces of an even older impact, around 4.472 billion years ago. This is what astronomers think - a massive body, about the size of Mars collided with Earth, eventually forming the moon. But about 5% of that debris from that collision was ejected back into space, where astronomers now think it smashed into asteroids in the asteroid belt.

So, scientists think that the rock that hit Lisa Webber's garage is actually a piece of debris from the very formation of the moon itself, a long strange trip.

We've also got news from space about one of earth's dirty secrets. Last week, the National Oceanic and Atmospheric Administration discovered that carbon tetrachloride, a chemical that was banned worldwide in 1987, is stilled being released into the atmosphere - a lot of it. Carbon tetrachloride is a chlorofluorocarbon, or CFC. We once used these chemicals a lot in things like aerosol sprays and foam food packaging.
But once in the atmosphere, CFCs break down and the resulting chlorine atoms attract oxygen atoms, breaking them off of ozone molecules. And we need those ozone molecules to absorb ultraviolet rays and protect earth's surface from harmful radiation.
By the 1980s, CFCs had depleted so much of the atmosphere's ozone that they were summarily banned. And for a while, scientists were relieved. They figured the CFCs would take about 25 years to break down or be absorbed by earth's oceans and soil so by now we should only have a small fraction of what there was before 1987. But instead of almost no carbon tetrachloride, NOAA found that around 39 thousand tons of it were still being released each year between 2007 and 2012. That's about 30% as much as was released during the peak emission years of the early 1980s.
Now, it could be that carbon tetrachloride just takes longer to break down that scientists thought. But more likely, someone is still releasing it and other CFCs into the atmosphere, ruining things, by which I mean the climate, for the rest of us.
NOAA says it needs to do more research to pinpoint the source of these nasty emissions like whether they're leaking out of old, contaminated sites or if they're being farted out by factories illegally.
Thank you as always for watching SciShow Space News, and if you want to keep exploring the universe with us, check out to learn how you can help support us and don't forget to go to and subscribe!