Get spooky (10/27/22)

Happy Thursday. Halloween’s about to get seriously spooky this year. A huge asteroid, about as wide as the height of the tallest building on Earth, is due to come whooshing by Earth, reaching its closest approach on November 1.

That “close” approach is still pretty far, at about six times further from us than the Moon. It’s not time to break out the doomsday gear just yet.

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X Marks the Spot

For millennia, humanity has been gazing up toward the stars, trying to make sense of the glittering madness. Hipparchus, a Greek astronomer who lived about 2,100 years ago, is credited not only with creating trigonometry, but also with assigning the first numerical coordinates to stars. The fabled star catalog itself was lost to the ages. We only knew it existed through the writings of Ptolemy, who lived ~400 years later.

Until now, that is.

In 2012, while examining a 146-page medieval Syric text called the Codex Climaci Rescriptus housed in the Museum of the Bible in Washington, DC, a student stumbled upon a bit of Greek text that had been erased and written over. Upon further examination, researchers identified the Greek passage—it had previously been attributed to the astronomer Eratosthenes, who holds credit for making the first measurement of the size of the Earth. 

Further examination ensued. The codex is a palimpsest, meaning it’s written on parchment that had been erased so it could be reused. In 2017, researchers took 42 photographs of each page of the codex, each in a different wavelength, trying to get a better picture of the faded, smudged Greek writing underneath.

A few years later, science historian Victor Gysembergh got a call from biblical scholar Peter Williams, who had been poring over the images. “I was very excited from the beginning,” Gysembergh told Nature. “It was immediately clear we had star coordinates.”

The first page the researchers deciphered contained the coordinates of the constellation Corona Borealis. It included the length and breadth, as well as the coordinates of the stars furthest in each cardinal direction. The coordinates line up with Ptolemy’s writings—and with real stellar coordinates.

Now, researchers are poring through the pages of the codex, looking for more star coordinates and further evidence that this document is, in fact, a piece of Hipparchus’ long-lost star catalog. 

(I, for one, am waiting with bated breath for more. Rumor has it he mapped the whole sky.)

Shaking it Up on Mars

For the first time ever, researchers have detected seismic waves on the surface of another celestial body.

On December 24, 2021, scientists working on the Marsquake Service at ETH Zurich recorded the unexpected quake using the seismometer on NASA’s InSight lander. Unlike the deep-seated rumblings kilometers below the surface they’d observed over the past three years, this quake traveled along the top layer of the planet’s crust.

The team set out to determine the cause of the high-riding quake. They reached out to researchers working with the Mars Reconnaissance orbiter to find out whether it had been caused by a meteorite strike rather than seismic activity. Lo and behold, the Orbiter team identified a meteorite that struck the Red Planet at the right time and region to cause the earthquake.

Though the impact came from an outside source, the Marsquake team was able to use this data to uncover details about the structure of the Martian crust. The speed that seismic waves move through a material is determined by the density and elasticity of that material. Initial observations showed that the waves moved through the ground much faster than the researchers expected given the point measurements previously taken by the InSight lander.

The meteorite impact from December caused the first surface seismic waves found on Mars, but not the last. In May of this year, InSight recorded a marsquake with a magnitude of 5 that also made ripples on the surface, giving researchers information about the top 90 km of Martian crust structure.

InSight is reaching the end of its life now. Its solar panels are covered in dust. These buzzer-beating observations were the team’s last shot at taking seismic observations from the lander, and there’s now plenty of analysis to be done to nail down the structure of the Martian crust.

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Other News from the Cosmos

• JWST snapped a pic of several large galaxies forming around a supermassive quasar.

• Chang’E 5, China’s 2020 lunar mission, returned samples that show volcanic activity helped form the Moon’s surface as recently as 2 billion years ago.

• DART’s impact on the asteroid Dimorphos created not one, but two trails of dust, Hubble observed.

• Climate change may be worsening the space debris problem by reducing the density of the upper atmosphere, allowing debris to face less drag and stay in orbit longer, according to a study from the British Antarctic Survey.

• An Earth-like exoplanet without an atmosphere orbiting a red dwarf star is helping scientists narrow down the search for extraterrestrial life.

• FAST, aka the Five-hundred-meter Aperture Spherical Telescope, observed a huge cloud of atomic gas ~2M light-years long in the region around Stephan’s Quintet.

• Carnegie Mellon researchers developed a methodology for balancing the risk and reward of exploring different regions of Mars with rovers.

Rachael's Recs

💥 SHIELD incoming! NASA’s got plans to go back to the Red Planet in style. And by style, I mean crash-landing. This feature from JPL explains why the agency is forgoing parachutes, jetpacks, and all manner of fancy Mars-landing equipment in favor of a good old tumble via its planned SHIELD lander.

👻 Quantum mysteries: What could be better than a little spooky action at a distance to get you in the Halloween spirit? In this op-ed for Scientific American, science journalist John Horgan beautifully explains the concept of quantum entanglement, and explores the history, mysteries, and contradictions surrounding its discovery.

The View from Space

Hubble's celebrating Halloween, too. This week, the telescope imaged the galaxy cluster Abell 611, which is a popular target for astronomers investigating dark matter.