What are asteroids made of? A sample returned to Earth reveals the Solar System's building blocks The meteorite samples could have been contaminated here on Earth, or their chemistry might have been changed by heating as they fell through the atmosphere. ![]() Uracil and other organic molecules have previously been found in these meteorites, but there has been no way to rule out the possibility that some of the molecules had a terrestrial origin. The Hayabusa2 mission established that C-type asteroids like Ryugu are the source of a kind of rare meteorite sometimes found on Earth, called a carbonaceous chondrite. These are the most common type in the asteroid belt, making up about 75% of the asteroids we can see. Ryugu is what’s called a C-type or carbonaceous asteroid. RNA is also made of a long string of bases: guanine, cytosine and adenine (like DNA), but instead of thymine it has uracil – which is what turned up in the sample from Ryugu. Life on Earth uses the structure of DNA to memorise the construction of the life form involved.Īlongside DNA, life uses a molecule called RNA for making proteins and doing other odds jobs inside cells. A strand of DNA also has a complex structure, which varies from one individual to another. ![]() Each base pair is made of two bases: either guanine and cytosine, or adenine and thymine.īuilding from the simple base pair chemicals to a full strand of DNA is a massive undertaking. The largest “chunk” of the human genome, chromosome 1, is made up of 249 million base pairs (the rungs on the twisted ladder of the DNA molecule). But this isn’t just a simple random combination exercise. Simple amino acids are believed to act as building blocks in the construction of these more complex molecules. The Hayabusa2 spacecraft is about to drop a chunk of asteroid in the Australian outbackĪt the most basic level, the development of life is a matter of combining simple organic molecules into increasingly complex compounds that can participate in the myriad reactions associated with a living organism.
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