If you’ve learned anything  from our Rocks Box videos, it’s that rocks tell us a lot about our planet.

But a select few rocks teach us about  a place much farther away: space! Meteorites are a treasure trove of  information about the solar system and beyond.

They can help us decode how the planets formed and provide tantalising clues  about life elsewhere in the cosmos. But meteorites are pretty rare, and the big, important ones that get studied  for decades are even rarer. So we’re gonna take a look  at four of the heavyweights, space rocks that changed  the way we see the universe. [♪ INTRO] First up is the Krasnojarsk meteorite,  a rock that helped European scientists realize that meteorites came  from space in the first place.

That wasn’t always stuff we knew. There are records dating back centuries  of Chinese and Egyptian scholars talking about metallic  objects falling from the sky, but it took far longer for the  Western scientific community to get that celestial memo. Why’d it take so long for  Europeans to get the message?

Well, it starts with Aristotle. Now obviously people had been  seeing rocks fall to the Earth since as long as there had been people. But back in 350 BCE, Aristotle  believed that space was filled with a substance called aether,  leaving no room for anything else.

As a result, he thought that  anything that fell to earth must have started out on Earth. He called them ‘exhalations’. I guess maybe he was a fan of breathing exercises.

It wasn’t until the enlightenment,  toward the end of the 18th Century, that this ancient idea was finally debunked. In the 1770s, an assistant to the  German naturalist Peter Pallas was travelling through Siberia  documenting rocks and fossils, when locals directed him  towards an awesome specimen: a nearly 800 kilogram lump of metal  embedded with glassy green minerals. We now call it the Krasnojarsk meteorite, but it wasn’t called that right away,  because nobody knew that it was from space.

All they knew was that it  was an extremely cool rock. Pallas had the rock hauled back to Europe, where he published a scholarly description of it. But he never imagined it had come from space.

Twenty years later, Pallas’ descriptions fell into the lap of another German  scientist, Ernst Chladni. Based on Pallas’s descriptions,  as well as eyewitness accounts of bright objects streaking through the sky, he proposed an extraterrestrial  origin for the meteorites. He claimed that they were the debris from  catastrophic collisions in outer space.

Of course, nobody at home believed  him, because everyone knew that there was nothing out  there in space besides the moon. But through the start of the 1800s, evidence started to accumulate in Chladni’s favor. Several more meteor falls were witnessed, and new mineralogical and chemical  analyses revealed that rocks like Pallas’s Siberian specimen were  completely unlike anything found on Earth.

Chladni was vindicated and Aristotle’s  stubborn idea was put to rest. The Krasnojarsk meteorite is a type  of meteorite called a pallasite, named after Peter Pallas himself. They contain both iron and rocky crystals, and we think that they form when an  asteroid fuses with the minerals of a planetary embryo, and that resultant  fusion-thing gets hurled back out into space.

So meteorites like this are even a window  into the interior of our own planet, where our drills and pickaxes will never reach. But our next famous meteorite is a window into the beginning of something  much bigger: our solar system. The Allende meteorite fell to Earth in 1969, where it broke apart over Chihuahua, Mexico.

More than two tons of rock  were immediately recovered, and thanks in part to its lucky timing, it became the most studied meteorite in history. In 1969, labs on Earth were poised to receive the first Apollo rock samples from the moon. Scientists and instruments were already  geared up to study extraterrestrial rocks, and so in a way, Allende became a  test subject for those approaches too.

Geochemists have measured its  oxygen isotopes, its trace elements, and superheavy elements, to  understand where it formed and how. It’s been examined using electron microscopes, x-rays and CT scans to help  understand its mineralogical makeup. And all of this testing helped us  understand how meteorites form, and how they change when exposed  to different environments.

And with the Allende meteorite, it also  revealed things that we never expected. Allende is a type of meteorite  known as a carbonaceous chondrite. These meteorites are usually made up  of tiny round grains called chondrules, as well as larger, irregular  shaped white inclusions.

The chondrules date from a  time in the early solar system when things were really messy. They’re basically frozen spherical  droplets of silicate minerals, which had been flash-melted when planets collided. Those minerals were then thrown  out into space where they instantly cooled and solidified, and then  gradually accreted together again.

However, there is a brand-new paper  that came out in June of 2026, while we were working on this video, that may call this hypothesis into question. The new paper suggests that the  chondrules and matrix all formed together at the same time in one chondritic reservoir, meaning that they could form  without a planetary collision. Regardless of which hypothesis wins, we know that these remarkable  asteroids are also incredibly ancient.

The light coloured inclusions  inside Allende are rich in aluminum, and contain minerals that only could have formed at extremely high temperatures close to the sun. Together, these inclusions  and the chondrules are some of the oldest solid matter in the solar system. Dating to 4.566 billion years  ago, the chondrite assembled under the rays of a newly ignited star, likely  before any other planets had formed.

But there’s more. Looking even more closely  at the Allende meteorite, researchers have found tiny  grains that predate our sun. Nanodiamonds and presolar graphite  grit inside this Mexican rock can be traced right back to  the explosive death of stars before our solar system was a  glimmer in the universe’s eye.

The Allende meteorite is indeed older  than the planet it ended up landing on. Allende may be the most popular meteorite  of its kind, but it’s far from the only one. Number three on our list  is the Murchison meteorite, another carbonaceous chondrite, which also  fell in 1969, but this time in Australia.

It’s a popular year for meteorites. Like Allende, it also contains presolar grains, and some researchers think that  they are around 7 billion years old. If so, they would steal the prize  for the oldest material on Earth.

But the rest of the meteorite  is made up of a dusty matrix which dates to around the  beginning of the solar system, and scientists discovered something entirely unexpected inside of it: organic matter. Yes, organic. As in, carbon-based.

As in, the stuff living things are made of. The meteorite contains amino acids,  sugars, hydrocarbons, and alcohols. Even some of the nucleobases which  are the encoding language of DNA.

In all, there are tens of thousands of different organic molecules hiding inside Murchison. In fact, there’s so much  organic stuff in this rock, it had a noticeable smell that some have  compared to compost or brussels sprouts. These organic molecules are  the building blocks of life, made by life since life began.

But as far as we know, there isn’t  any other life in the solar system. So what’s going on with Murchison? Well, even if we call it organic chemistry, life isn’t the only thing that  can make these molecules happen.

It’s thought that the smaller,  simpler molecules were created thanks to the chance chemical reactions  in the interstellar medium early on in the solar system’s history, when  there was more stuff around to combine. These early creations then accreted  along with the rocky components of Murchison, and then were further altered  by UV radiation in the meteorite itself. Over its long history, the asteroid  that gave birth to Murchison was also permeated with water at several points, caused by radioactive heating melting  ice crystals inside its structure.

This liquid water helped to create  even more organic molecules. Studying Murchison, and theorizing  about its formation in the lifeless early solar system, has shown us that the building blocks of life are  not unique to living things. This has helped us question our  theories about the origin of life, and raised the possibility that some  of the very first organic chemistry actually originated among the  stars, rather than here on Earth.

Which brings us to our fourth and final meteorite. Did you know it was coming? I did.

Because some people believe that it contains  evidence of real extraterrestrial life. Found in the Allan Hills  region of Antarctica in 1984, ALH84001 is a Martian meteorite. Formed by volcanic lava more  than 4 billion years ago, it was ejected after an  impact 16 million years ago, and arrived on Earth around 13,000 years ago, to sit on the white Antarctic ice until  explorers wandered by and picked it up.

What a legacy. You know, if I was gonna be a  rock, that’s the one I’d wanna be. But its biggest moment came in 1996, when a controversial paper was published  claiming it contained microfossils.

Electron microscope images show  a tiny track of magnetite disks, that looked a lot like trails  that bacterial decomposers leave behind as they navigate. Additionally, chemical analysis  revealed that the meteorite contained a specific kind  of organic molecule called polycyclic aromatic hydrocarbons, which on Earth are produced by decaying organic matter. Almost immediately, people were swept up in the excitement of discovering life on Mars.

Then-president Bill Clinton even made  an announcement about the discovery. I was at summer camp. I was so mad I couldn’t blog about it.

So that’s where we’re at. But a lot of the scientific  world was more skeptical. For one thing, the worm-like  shape that seemed so convincing is basic enough that non-biological  processes can make it too.

So the resemblance to earthly  microbes is probably a coincidence. Also, those polycyclic aromatic  hydrocarbons are formed by life, but not only by life. They’re also found in things like car  exhaust and interstellar gas clouds.

It also seems like it was heavily altered  by water-rock interactions while on Mars, which could be the source of both the  organic molecules and the magnetite. There’s also a good chance it got  some good old Earthly contamination, after the rock spent 13,000 years out in  the open on the Antarctic ice surface. Today, most researchers agree that  ALH84001 does not contain evidence of life on Mars, but it does still contain  lots of information about the red planet.

The minerals inside the meteorite  reveal the presence of liquid water, and specifically water that  was at a low temperature and of a neutral or weakly alkaline pH. Not only that, but it contains clay minerals, which are thought to have  been important catalysts for early biochemical reactions on Earth, meaning that they could have  performed the same role on Mars. So even if it’s not proof of life on Mars,  this meteorite is still pretty far out.

These meteorites are just a few of  the tens of thousands that have been found on Earth, and which continue  to rain down on our planet every day. They’ve helped transform what we know  about life, the universe and everything. And Rocks Box subscribers will  receive a piece of this legacy when they get these pieces of a  meteorite from Northwest Africa.

We’ve been running the Rocks Box  subscription for more than two years now, and the feedback from our  subscribers has been amazing. And luckily for those of you who’ve been  waiting for more subscriptions to open up (there are not that many because of course we actually have to source these things), but we now have room in the  Rocks Box for new people to join. Whether you’re a seasoned rock hound  or just starting out your collection, SciShow Rocks Box might be just  the monthly treat that you need.

Or maybe you’ve got a friend  who’s mineral-curious, or a relative who is just impossible to shop for. If so, head over to  Complexly.store/rocks to check it out. We also sell some fan  favorite minerals as one-offs.

Plus, there are accessories  like this jeweler’s loupe so that you can get more up close  and personal with your rocks. There’s a whole lot more as well. That’s Complexly.store/rocks.

Thanks for watching! [♪ OUTRO]