A new study suggests that Earth may unknowingly be alerting extraterrestrial civilizations (Aliens) to its presence. The research shows that deep-space radio transmissions—especially those directed at spacecraft near Mars—spill beyond their intended targets. If alien observers were aligned with certain planetary positions, they could detect these signals.
The findings imply that by mirroring this approach—targeting exoplanet alignments—scientists could improve the search for extraterrestrial technosignatures.
How Our Signals Leak Into Space
Researchers from Penn State and NASA’s Jet Propulsion Laboratory (JPL) analyzed logs from NASA’s Deep Space Network (DSN), a global system of antennas used to communicate with spacecraft. The analysis revealed that most transmissions are directed toward Mars and other interplanetary spacecraft.
Because planets like Mars do not completely block radio signals, transmissions often spill over into space. Extraterrestrial observers located along these paths—when Earth and Mars align from their perspective—would have a higher chance of intercepting them.
“Humans are predominantly communicating with spacecraft near Mars,” explained Pinchen Fan, graduate student at Penn State and lead author of the paper. “But a planet like Mars does not block the entire transmission, so distant observers could potentially detect the spillover.”
When and Where Aliens Could Detect Us
The study found a 77% chance of extraterrestrial observers being in the signal path. This applies if they were located where they could see Earth and Mars align. For alignments with other planets, the chance dropped to 12%.
Outside of alignments, however, the chances of detection were very low. Joseph Lazio, project scientist at JPL, emphasized the importance of the DSN: “It sends some of humanity’s strongest and most persistent radio signals into space, and its public logs let us map their patterns over the past 20 years.”
Lessons for Our Own SETI Searches
The research suggests that Earth’s transmission patterns could guide how humans search for extraterrestrial intelligence. Instead of scanning randomly, scientists could focus on exoplanet alignments, where alien civilizations might also broadcast their own signals.
Astronomers already study exoplanets when they align with their host stars. The upcoming Nancy Grace Roman Space Telescope is expected to vastly expand known exoplanet catalogs. It will increase the number of potential targets for SETI.
Jason Wright, director of the Penn State Extraterrestrial Intelligence Center, noted: “Using our own deep-space communications as a baseline, we quantified how SETI searches could be improved by focusing on planetary orientations and alignments.”
How Far Our Signals Travel
The team calculated that an average DSN transmission could be detected up to 23 light-years away. This estimation uses technology comparable to ours. Scientists could focus searches on nearby solar systems within this range. These systems should be oriented edge-on to Earth. This focus would maximize the chances of detecting alien technosignatures.
Looking Ahead
As humanity sends more missions deeper into space, radio transmissions will only increase. This could make Earth even more detectable to alien civilizations in the future.
The research was published on August 21 in The Astrophysical Journal Letters. It was supported by NASA’s Exoplanets Research Grant Program and Penn State’s Extraterrestrial Intelligence Center.
