A new scientific study has demonstrated that the most promising moments to detect extraterrestrial civilizations are during planetary alignments, when deep space communication systems are most active and their signals are most likely to spill into interstellar space. The findings come from a detailed analysis of NASA’s Deep Space Network, published in The Astrophysical Journal Letters in September 2025, and provide the clearest evidence yet that Earth itself is already broadcasting detectable signals in structured patterns that could be intercepted by other civilizations.
The research team, led by Pinchen Fan of Penn State along with Jason Wright and Joseph Lazio of NASA’s Jet Propulsion Laboratory, examined twenty years of transmission logs from NASA’s global Deep Space Network, which operates powerful radio antennas in California, Spain, and Australia. These facilities are responsible for maintaining communications with spacecraft throughout the solar system. Every command sent to a planetary probe, every stream of data returned from an orbiter, and every routine contact with a telescope beyond Earth’s orbit involves the use of these antennas. Each transmission is aimed at a spacecraft target, but the radio energy continues outward indefinitely into space.
The researchers mapped the pointing directions of the transmissions and recorded how long each region of the sky had been illuminated, calculating the duty cycle for every point. Between January 2005 and January 2025, the antennas covered approximately fifteen percent of the celestial sphere. The analysis revealed that the distribution of signals is far from random. Nearly eighty percent of transmission time was concentrated within five degrees of the ecliptic plane, which is the flat plane defined by Earth’s orbit and shared by the other planets. For any observer located near this plane, Earth would already appear as an active source of radio transmissions.
The duty cycle within the Earth Transit Zone, the narrow strip of sky from which Earth would be seen passing in front of the Sun, was found to be about twenty times higher than the average across all latitudes. This means that a civilization located in that zone would have far greater opportunity to detect Earth’s transmissions than one located elsewhere. The concentration is explained by the fact that most spacecraft are launched and operated close to the ecliptic, so antennas are almost always pointed within a few degrees of this plane.
The strongest concentration was observed along the Earth–Mars line. Because of the continuous presence of orbiters, rovers, and landers at Mars, the Deep Space Network has maintained an exceptionally high level of communication with the planet. The analysis shows that during Earth–Mars conjunctions, when the two planets align, a distant observer situated on that line would have had a seventy-seven percent chance of intercepting a transmission in the past twenty years. This represents an increase in detectability by a factor of four hundred thousand compared to random chance.
The study also found that the duty cycle within two arcminutes of Mars reached seventy-seven percent, equivalent to more than nine months of transmissions per year. Even between two and three arcminutes away, the duty cycle was still fifty-eight percent, or about seven months per year. Outside of that range, the probability dropped sharply. This pattern makes Mars the single most illuminated target of human space activity, effectively serving as a beacon for any civilization positioned along the Earth–Mars line.
The researchers extended their analysis to other planets. Weaker but still noticeable peaks were observed for Mercury, Jupiter, and Saturn, reflecting periods when missions to those planets were active. The James Webb Space Telescope at the Sun–Earth L2 point produced a significant increase in transmissions opposite the Sun, particularly in the years 2022 to 2024. Other observatories at Lagrange points, such as SOHO and DSCOVR, also accounted for dense clusters of signals. These long-term operations created sustained concentrations of transmissions that could be recognized by an external observer as structured and artificial.
Using standard radiometric calculations, the team estimated the detectability of a typical Deep Space Network transmission. With a 70-meter dish transmitting in the X band at 20 kilowatts for a three-hour session, and assuming a one-kilohertz bandwidth, the signal would be detectable with a signal-to-noise ratio of five by the Green Bank Telescope from a distance of seven parsecs, or about 23 light years. Within that distance lie 128 known star and brown dwarf systems. Any civilization in those systems with similar or better instruments could already detect Earth’s transmissions.
The actual detectability could be even higher. Previous studies have suggested that under different conditions, such as narrower bandwidths or larger receiving instruments, Deep Space Network transmissions could be detected from several tens of parsecs away. An extraterrestrial intelligence with advanced technology could potentially hear Earth from much farther distances. Conversely, Earth-based telescopes could use the same methods to search for analogous networks operated by other civilizations.
The authors emphasized that the detectability of transmissions is not uniform across the sky. By plotting duty cycles across different coordinates, they showed that the highest probability regions coincide with planetary conjunctions and alignments. For observers located along these lines, the probability of intercepting a signal is increased by many orders of magnitude. In the case of Earth–Mars conjunctions, the amplification is four hundred thousand-fold. When Earth is directly behind another planet as seen from the outside, the chance of detection rises to twelve percent, a sixty-thousand-fold increase compared to random chance.
These findings suggest that the best SETI targets are exoplanetary systems oriented edge-on to Earth, particularly those with transiting planets. In such systems, the orbits are nearly coplanar with our line of sight, increasing the chance that their own deep space transmissions would cross Earth’s view. Observing those systems during planetary conjunctions or occultations could dramatically improve the odds of detection.
The researchers noted that future expansions of human activity will only strengthen these patterns. As more spacecraft are deployed to Mars and other planets, and as human missions begin to operate for longer durations, transmissions will become more continuous and more powerful. Planned optical communication networks, using lasers, will have even narrower beams, but any leakage will still follow the same geometry. Planetary alignments will remain the moments when technosignatures are most detectable.
The study also pointed out that other spacefaring nations are developing their own deep space communication systems. China’s Deep Space Tracking, Telemetry, and Command system, for example, is capable of transmitting at up to 18 kilowatts in the S band and 15 kilowatts in the X band. Similar systems in other countries will contribute additional patterns. Although the current analysis focused on NASA’s Deep Space Network, the overall distribution of humanity’s deep space transmissions is likely even broader.
Because the logs used in the analysis did not always include exact power levels, the study focused on directional patterns and duty cycles rather than absolute flux values. However, data obtained through private communication confirmed that approximately half of the transmissions were around 20 kilowatts, with the rest below that level. For Mars, a small subset of data showed about one-third of transmissions at 20 kilowatts and the remainder lower. Even at those levels, the signals are strong enough to be detected across interstellar distances.
The authors concluded that Earth has already reached the point where its deep space communications are visible from outside the solar system. The concentration of transmissions within the ecliptic plane, the high duty cycle toward Mars, and the structured patterns around Lagrange points all constitute detectable technosignatures. For SETI researchers, this means that analogous strategies should be applied when searching for extraterrestrial intelligence. By focusing on planetary alignments and conjunctions, astronomers can maximize the likelihood of intercepting signals from civilizations operating deep space networks similar to our own.
Over the twenty years of data examined, humanity’s antennas have swept beams across fifteen percent of the sky, but the effective detectability is not spread evenly. It is clustered, predictable, and governed by planetary geometry. For those monitoring from beyond, the moments when planets align are the times when Earth is most exposed. For those on Earth searching outward, those same alignments in other systems represent the best chance of discovery.
