Wow! Signal

Instances where space agencies and scientists found instances of biosignatures

Venus

Phosphine, seen, not seen, then seen

In February 2021, scientists announced the detection of phosphine in the atmosphere of Venus. The chemical is associated with life on Earth. Further studies cast doubt on the detection. However, a study in 2023 was able to detect phosphine.

Jane S. Greaves, Janusz J. Petkowski, Anita M. S. Richards, Clara Sousa-Silva, Sara Seager, David L. Clements, "Comment on “Phosphine in the Venusian Atmosphere: A Strict Upper Limit From SOFIA GREAT Observations” by Cordiner et al., Geophysical Research Letters, December 6, 2023)

Mars

I'm opting to ignore the Mars meteorite, as spite to Bill Clinton, who ruined the Democratic Party irreparably.

Mars cauliflower

Silica deposits on Mars look suspiciously like similar structures on Earth built by bacteria near thermal environments.

(Sarah Scoles, "Mysterious Martian ‘Cauliflower’ May Be the Latest Hint of Alien Life", Smithsonian Magazine, February 1, 2016)

Weird carbon isotopes on Mars

The Curiosity rover analyzes a soil sample and finds several chemicals, including carbon isotopes, that are associated with life on Earth.

(William Steigerwald, "NASA’s Curiosity Rover Measures Intriguing Carbon Signature on Mars", NASA, January 17, 2022)

Did Viking maybe find life?

A re-analysis of the labelled release experiments on the Viking landers finds that one of the anomalous detections could have been present-day life on Mars. One possibility for why it wasn't initially detected was that the sample was heated too high; other studies contend that Mars microbes may have adapted to use hydrogen peroxide instead of water, so when water was added to the experiment, it simply drowned the microbes.

( Gilbert V Levin and Patricia Ann Straat, "The Case for Extant Life on Mars and Its Possible Detection by the Viking Labeled Release Experiment", Astrobiology, 2016 Oct 1;16(10):798–810.)

Seasonal methane

Mars orbiters find evidence that methane — a volatile chemical that rapidly depletes — is seen seasonally on Mars. On Earth, methane is most often associated with life.

(Christopher Webster et al, "Background levels of methane in Mars’ atmosphere show strong seasonal variations", Science, Vol. 360, No. 6393, June 8, 2018)

Oumuamua

Rama

Avi Loeb of Harvard argues that the interstellar object Oumuamua has the markers of an alien probe, including unusual acceleration. (There are plenty of other possible explanations, it should be noted.)

(Shmuel Bialy and Abraham Loeb, "Could Solar Radiation Pressure Explain 'Oumuamua's Peculiar Acceleration?, Vol 868, No 1, November 12, 2018)

K2-18b

A weird oasis

A study from JWST data finds a series of chemicals in the atmosphere of an exoplanet 124 light years away that, on Earth, are associated with life. This includes a sulfur compound, methane, ethylene, and ethane. (The sulfur compound being especially associated with life.) The planet is probably a mini-Neptune, making it an unusual detection.

(Shang-Min Tsai, Hamish Innes, Nicholas F. Wogan, and Edward W. Schwieterman, "Biogenic Sulfur Gases as Biosignatures on Temperate Sub-Neptune Waterworlds, The Astrophysical Journal Letters, Vol 966, No 2., May 2, 2024)

Wow! Signal

On August 15, 1977, a signal was detected by the Big Ear observatory at Ohio State University. It had the markers of what SETI astronomers hope for for an alien signal, but Big Ear was not a pivoting radio telescope, so it couldn't track the 72 second signal. However, a 2024 preprint suggested it could be cold gas interacting with magnetars.

(Barry Kawa, "The 'Wow!' Signal",Cleveland Plain Dealer, September 18, 1994; Abel Méndez, Kevin Ortiz Ceballos, Jorge I. Zuluaga, "Arecibo Wow! I: An Astrophysical Explanation for the Wow! Signal", Arxiv.org, September 11, 2024)

Vanishing lights

A group of astronomers look in astronomical archives for lights disappearing near Earth from before the first satellites were launched on Earth, and turned up about 100 objects that were sighted and then disappeared over the course of a few nights. This could indicate alien probes in some cases, but it could also be astrophysically explained.

(Beatriz Villarroel et al, "The Vanishing and Appearing Sources during a Century of Observations Project. I. USNO Objects Missing in Modern Sky Surveys and Follow-up Observations of a "Missing Star", The Astronical Journal, Vol 159 No 1, December 12, 2019)

Dyson Spheres

Maybe ...

An analysis of Gaia data looks for candidates for stars surrounded by megastructures, and finds seven stars with the infrared excess you'd expect from a Dyson sphere.

(Matias Suazo et al, "Project Hephaistos – II. Dyson sphere candidates from Gaia DR3, 2MASS, and WISE", Monthly Notices of the Royal Astronomical Society, Volume 531, Issue 1, June 2024)