On the origin of our species

For the first time in history, scientists have detected the presence of one of the four nucleobases of RNA on an asteroid in space, per a peer-reviewed study published yesterday in Science Advances.

And if your first thought was “aliens!” a) you’re not alone and b) yes, aliens – but probably not the ones you’re thinking of. The discovery, based on samples taken from the asteroid Ryugu by a Japanese spacecraft in 2019, represents the strongest evidence yet that the building blocks for life first came to Earth from outer space.

☄️➡️👩 A deeper dive… RNA, like DNA, is present in all living cells and made up of four total nucleobases. The presence of one of those nucleobases – uracil – was detected in the Ryugu samples.

While uracil has previously been found in samples taken from meteorites, those objects had already landed on Earth before they could be analyzed. This left open the possibility that they had already been contaminated by humans, or our planet’s atmosphere.

• But because the Ryugu rock samples were collected in space nearly 2 billion miles from Earth, Japanese scientists were able to confirm the presence of uracil on asteroids for the first time.

🧬 Bottom line: One of several theories about the origin of life suggests that RNA first arose before DNA, and that early living organisms relied on RNA for the chemical reactions associated with life. So if the building blocks for RNA can be found in space, it lends credence to a separate (but complementary) theory suggesting life first came to Earth on comets and asteroids.