Planet killer (11/3/22)

Good afternoon, and happy Thursday. Yesterday marked 22 years that team humanity has maintained a constant presence in space. Here’s to many more years to come.

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The Planet Killer

Peering through the light-warping haze of the atmosphere at twilight, astronomers made a rare discovery: Three huge near-Earth asteroids, each capable of causing the next mass extinction event on Earth.

Now, before I get ahead of myself, these asteroids aren’t headed for Earth. Two of the three will orbit completely inside Earth’s orbit, never crossing, in perpetuity. There’s a small possibility that the third, 2022 AP7, could end up on a collision course with us sometime in the next couple thousand years—but that’s a later us problem.

The discovery of these asteroids was lucky because of their location within Earth’s orbit. To date, researchers have identified ~27,000 near-Earth asteroids. Only about 25 of those orbit between the Earth and Sun. 

The glare from the Sun makes it incredibly difficult to spot faint objects like asteroids from ground-based instruments between the Earth and Sun, and impossible from space telescopes, which have to face away from the Sun so they don’t fry their instruments.

For the Víctor M. Blanco four-meter telescope at Cerro Tololo Inter-American Observatory in Chile, operated by NOIRLab, timing is everything. There are only two 10-minute windows each evening when the lighting conditions are dim enough that the telescope can survey the horizon for asteroids lurking in the Sun’s direction.

And at those times, the telescope has to look through the Earth’s atmosphere, which distorts its observations and adds another layer of complexity for researchers hoping to spot faint objects.

Though looking for asteroids between the Earth and Sun is a tough task, scientists have high confidence that they’ve done it well. At this point, there are probably only a few “planet killers,” or asteroids larger than ~1km across, left to find, lurking somewhere in the Sun’s vibrant glare.

Happy hunting.

It's meeeeeeeeeeeelting

Satellite imagery is giving researchers a clearer window than ever into what’s happening in one of the most frigid, remote regions on Earth: the Arctic. 

In a new study published Monday in Arctic, Antarctic, and Alpine Research, researchers at Colgate University used off-the-shelf commercial imagery from Planet and WorldView to pinpoint the time of year that meltwater ponds begin to form in the Arctic along with when they freeze back up again.

The findings? Ice in the Arctic's summer thaw begins about a month earlier than previously thought, and stays melted for two months longer than expected.

“What’s even more fascinating is that this ground is thawing and staying thawed at temperatures below freezing, so we know salts must be helping it to melt and keeping it muddy, like salting a road during a snowstorm,” Joseph Levy, a researcher on the project, said in a press release.

Meltwater ponds are home to hardy microorganisms that rely on liquid water for survival. The prolonged thaw is likely great for these critters, but may show signs of trouble for the longevity of the permafrost, the researchers noted.

The big picture: The increased availability of frequent satellite imagery with wide coverage is making this kind of research far easier to carry out. Not too long ago, researchers had to rely on an occasional image from a civil science satellite or trek out to the field to make measurements. Now, the accessibility of frequent, high-resolution satellite imagery can make Arctic ice research more timely, accurate, and robust.

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Other News from the Cosmos

• Tiangong, China’s orbital space station, is officially complete. The last module docked earlier this week.

• Edward Stone, the project manager for the Voyager missions for the past half century, has retired from NASA.

• ALMA, a powerful observatory in the Chilean Andes, fell victim to a cyberattack on Saturday that took its systems offline.

• The IceCube Neutrino Observatory identified the nearby galaxy NGC 1068 as a point source for high-energy neutrinos.

• NASA launched a citizen science project to capture images of sprites, the unexplained electrical phenomena that sometimes appear as the ghosts of lightning bolts.

• Researchers at the University of St. Andrews formed a hub to prepare humanity for potential contact with extraterrestrial life.

• A vent site uncovered in the Arctic makes a great natural laboratory for studying abiotic organic synthesis—a useful area for understanding the possibility of life on other planets.

• Goethe University researchers created a computer model to understand what happens during a collision between neutron stars.

• China’s Dark Matter Particle Explorer (DAMPE) found evidence that dark matter moves more slowly than previously expected.

• EMIT, aka the Earth Surface Mineral Dust Source Investigation, has identified more than 50 methane “super-emitters” across the globe.

Rachael's Recs

📈 Growing pains: The universe is expanding, that’s for sure. But how fast? Analyzing different types of data yields two very precise yet oh-so-different values for the Hubble constant, which estimates the speed of the universe’s expansion. In this article for Big Think, scientist and writer Don Lincoln explores the so-called Hubble tension and how it may be explained.

⚡ Take cover: The Sun is constantly bombarding us with radiation, and its solar flares and coronal mass ejections can wreak havoc on electronics that aren’t prepared to withstand it. In a long-form article for the BBC, reporter Chris Baraniuk explains what goes wrong when a cosmic ray strikes in the wrong place.

The View from Space