• This was a cool study positing that the Earth passed though a dense interstellar cloud 2-3 million years ago. It was a clever use of computational modeling to recreate the paths of our solar system and the Local Ribbon of Cold Clouds through millions of years. From commentary in the Harvard Gazette re. the study by Opher and Loeb in arXiv.

“The evidence exists in the form of noticeable peaks in the deposition of two radioactive isotopes: iron 60 and plutonium 244. Both are very rare, created when massive stars explode in supernova. Those isotopes are thought to be more plentiful in the interstellar medium.

“It is everywhere, in the deep ocean, on the moon, on ice in Antarctica,” Opher said. “These papers describe a global phenomenon. Something happened. And iron 60 is not produced on Earth. So I knew that somehow this iron 60 got trapped in dust, and somehow, 2 to 3 million years ago, we had more dust delivered to us.”… “Our work should trigger more studies into this question,” Loeb said. “It draws attention to our cosmic neighborhood as having potential influence on life on Earth. We usually tend to just look at it and enjoy it, but we are actually moving through interstellar space, and there could be risks along the way.””