Father-daughter team decodes 'alien signal' from Mars that stumped the world for a year

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A father and daughter team based in the U.S. have decoded a mock "alien signal" beamed from ESA's ExoMars Trace Gas Orbiter a year ago — but the meaning of the extraterrestrial message remains a mystery.

A digital image with a black background and white symbols that resemble molecules
A radio signal beamed to Earth last year by ESA’s ExoMars Trace Gas Orbiter contained this image depicting five amino acids. Citizen scientists Ken and Keli Chaffin were the first to decode the image from the radio data. (Image credit: Ken and Keli Chaffin)

A father-daughter team has decoded a mock "alien" message after a year of trying. Now, citizen scientists are trying to figure out what the decoded missive truly means for Earth.

According to the European Space Agency (ESA), Ken and Keli Chaffin from the U.S. were the first to crack the code, which was sent from ESA's ExoMars Trace Gas Orbiter as part of a citizen science project in May 2023. Three radio observatories on Earth heard the message, and the data were made available to the public. The first step was to extract the signal from the raw data, and the second was to decode it.

The message turned out to be an image depicting the structure of five amino acids, the building blocks of proteins. It was the brainchild of a group of "simulated extraterrestrials," according to A Sign in Space, which included de Paulis, as well as a computer scientist, a poet, a radio engineer, a physicist and space lawyer, and several astronomers and astrobiologists.

Related: Infamous 'Wow! signal' that hinted at aliens may actually be an exceptionally rare cosmic event

The project had additional support from the SETI Institute — a nonprofit dedicated to the search for extraterrestrial life — and the Green Bank Observatory in West Virginia. Decoding the message required many hours of computer simulations. The Chaffins managed to crack the code when they figured out that the message included some biological features, ESA reported.

But what would aliens be trying to convey by sending a picture of five amino acids? That mystery still needs to be solved. Now, citizen scientists are gathering on a Discord server to debate and puzzle over the message's meaning. Do aliens come in peace? That question might be the toughest to answer.

Stephanie Pappas
Stephanie Pappas
Live Science Contributor

Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.