Vital signs (6/15/23)

Good afternoon, and happy Thursday. Another week, another missed opportunity for Betelgeuse to explode.

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Building Blocks of Life on Enceladus

Life, we believe, is rare in the universe. The hunt for living beings originating outside of Earth remains one of the core goals of modern astronomy, and every day, scientists turn countless instruments to the cosmos, searching for habitable worlds and signs of life.

New findings pulled from Cassini probe observations provide a glimmer of possibility that life beyond Earth is closer than we thought. A study published yesterday in Nature describes the finding of phosphorus in a watery plume erupting from the surface of Saturn’s icy moon Enceladus.

To be clear, phosphorus itself is not necessarily a biomarker. “High phosphate concentrations are a result of interactions between carbonate-rich liquid water and rocky minerals on Enceladus’ ocean floor and may also occur on a number of other ocean worlds,” Christopher Glein, a coauthor and planetary scientist at the Southwest Research Institute, said in a release.

What it is, though, is an important foundational element for the formation of life. Its presence—and even, potentially, abundance—beneath the surface of Enceladus makes the moon a promising hunting ground for astrobiologists.

Cassini’s hunt: On its mission to Saturn’s system of rings and moons, NASA’s Cassini probe collected data on the particles it came across. In 2008 and 2009, it had sampled particles that erupted in an icy plume from Enceladus into space, and NASA has held onto those observations in its Planetary Data System.

New analysis of the data revealed a high concentration of sodium phosphates in those plumes. The team of researchers used these findings to conclude that Enceladus’ ocean contains phosphorus in concentrations at least 100 times more than is present in our own planet’s oceans.

Reader, beware: We’ve gotten overzealous about findings of phosphates in our solar system before. In 2020, a team of astronomers conducting observations of Venus using the ALMA telescope in Chile reported that they had found phosphine in the planet’s upper atmosphere.

• Phosphine, or PH₃, is only formed through biological processes on Earth, including through some anaerobic respiration and as organic matter decays.

• It’s been found in the atmospheres of Jupiter and Saturn, too, where it was likely formed in the gas giants’ intense internal environments, but there’s no known geological process that could explain the presence of phosphine on Venus.

The scientific community erupted, calling for follow-ups to confirm whether or not there might be life residing in those dense clouds. NASA followed up last year with the now-defunct SOFIA (Stratospheric Observatory for Infrared Astronomy) aircraft. The observatory could not corroborate the finding of phosphine.

Looking forward: The abundance of such an essential element for life as we know it in Enceladus’ vast subsurface ocean—and possibly in the subsurface oceans of other moons in our solar system—is an exciting prospect as we search for life in our celestial neighborhood. Cassini ended its mission in 2017, plunging into the depths of Saturn, and was one of only four probes ever to visit the planet.

There are currently no missions planned to visit Enceladus in the near future, so for now, follow-up studies will need to be conducted from afar, if at all.

Other News from the Cosmos

• Earth may have formed much more quickly than previously thought, within just a few million years, through rapid pebble accretion.

• Exoplanets may not need to have plate tectonics for life to emerge.

• Rock-forming elements in the atmosphere of the distant gas giant WASP-76b leave clues to how these types of planets form.

• Dark matter may be composed of hypothetical ultra-light particles called “axions,” which are linked to the clumpy overall structure of the universe.

• The first batch of DESI (Dark Energy Spectroscopic Instrument) has been released, including information on more than two million individual galaxies, quasars, and stars.

• The solar corona is hotter than the Sun’s surface. Intense wave activity in the star’s coldest regions, the sunspot umbras, could explain why.

• Pluto and its largest moon, Charon, form a binary system around which four other objects orbit.

The View from Space

Here’s a throwback from Hubble, depicting the interacting galaxies Arp 273.