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Showing posts from August, 2021

Deflecting an Asteroid Before It Hits Earth May Take Multiple Bumps

[ https://www.nytimes.com/2021/08/25/science/asteroid-deflection-collision.html ] Source: By Katherine Kornei , The New York Times.  Excerpt: There’s probably a large space rock out there, somewhere, that has Earth in its cross hairs. Scientists have in fact spotted one candidate —  Bennu, which has a small chance of banging into our planet in the year 2182 . But whether it’s Bennu or another asteroid, the question will be how to avoid a very unwelcome cosmic rendezvous. For almost 20 years, a team of researchers has been preparing for such a scenario. Using a specially designed gun, they’ve repeatedly fired projectiles at meteorites and measured how the space rocks recoiled and, in some cases, shattered. These observations shed light on how an asteroid might respond to a high-velocity impact intended to deflect it away from Earth. At the 84th annual meeting of the Meteoritical Society held in Chicago this month, researchers  presented findings from all of that high-powered marksmansh

Ancient supernovae might have upended Earth’s evolution

https://www.sciencemag.org/news/2021/08/ancient-supernovae-might-have-upended-earth-s-evolution By  Claire Hogan , Science Magazine.  Excerpt: When stars run out of fuel, they can collapse under their own gravity, exploding as supernovae that blast debris and radioactive nuclei far into space. Most of these events are too far from Earth to affect our planet. But if one happened nearby,  the effects could be dramatic . By studying radioactive isotopes on Earth, scientists have uncovered evidence suggesting two near-Earth supernovae occurred in the past few million years. Some researchers now hypothesize that supernova-generated particles known as cosmic rays might have depleted the ozone layer, increased cancer rates in ancient organisms, sparked wildfires, and even started an ice age....

‘Totally new’ idea suggests longer days on early Earth set stage for complex life

By  Elizabeth Pennisi , Science Magazine.  Excerpt: Today, oxygen fuels much of life on Earth, but it wasn’t always that way. Three billion years ago, this gas was scarce in the atmosphere and oceans. Knowing why oxygen became plentiful could illuminate the evolution of our planet’s flora and fauna, but scientists have struggled to find an explanation satisfying to all. Now a research team has proposed a novel link between how fast our planet spun on its axis, which defines the length of a day, and the ancient production of additional oxygen. Their modeling of Earth’s early days, which incorporates evidence from microbial mats coating the bottom of a shallow, sunlit sinkhole in Lake Huron, produced a surprising conclusion: as Earth’s spin slowed, the resulting longer days could have triggered more photosynthesis from similar mats, allowing oxygen to build up in ancient seas and diffuse up into the atmosphere.  That proposal , described today in Nature Geoscience, has intrigued some sci