A new analysis by researchers at Penn State and NASA's Jet Propulsion Laboratory takes a closer look at where and when alien civilizations might catch signals from Earth, reports IFL Science. The study, published in Astrophysical Journal Letters and discussed at the 2025 Penn State SETI Symposium, maps out the patterns of our most detectable deep-space transmissions, suggesting these patterns could also point SETI (search for extraterrestrial intelligence) researchers to the best spots for hunting for extraterrestrial signals, per a release.
According to lead author Pinchen Fan, human radio transmissions to interplanetary spacecraft—such as those orbiting Mars—could be noticed by alien observers, should they exist. When Earth aligns with other planets, there's potential for these communications to "spill over" into space, making them more detectable to a distant onlooker. Fan notes that this same logic could be flipped, helping guide future SETI searches by focusing on moments of planetary alignment outside our solar system.
The team examined two decades of logs from NASA's Deep Space Network, the main system for sending and receiving messages to and from interplanetary spacecraft and telescopes. While other countries also have deep space networks, NASA's DSN is considered representative of most communications emerging from Earth due to its broad mission portfolio. Project scientist Joseph Lazio emphasizes that the network sends out some of humanity's "strongest and most persistent" signals, allowing the researchers to map out both when and where these emissions are most prominent.
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The study limited its focus to deep space transmissions, ignoring signals to satellites or spacecraft in low earth orbit, as those are weaker and less likely to be detected across great distances. By tracking the direction and frequency of the most common signals, the researchers say we can better estimate where, and perhaps when, to listen for evidence of alien technology.
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