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Despite the (ahem) creative interpretations that have been made of some of our space audio recordings, we have never recorded anything that could be explained as intelligent alien signals. We have, however, recorded voices in space . . . at Earth. This recording was made 1996-05-29 02:56 UTC by the PWI instrument on the NASA Polar spacecraft. We were flying in a very rare trajectory following a magnetic field line and picked up what is presumed to be Russian VLF maritime communications. Normally these frequencies would be blocked by the ionosphere and only the rare geometry of our trajectory allowed these signals to be detected. The primary feature (other than the female voice) is the hiss from the magnetospheric polar cusp region. The video comes from JHUAPL computer animation by Steven P. Gribben (copyright 2004) of the Polar spacecraft and is not related to the audio except that it illustrates the fact that the spinning spacecraft alternately picks up stronger cusp emissions as the antenna power pattern sweeps through the direction of the source twice per rotation. Comments published when this audio was originally released in 2004: “On the sounds from space website we confirmed that there are Earth-based radio emissions superposed at times. They occur intermittently at times between about 02:56:13 and 02:56:38 on May 29th, 1996 and lie at frequencies that extend to about 6 kHz. Earth-based radio emissions are occasionally observed by satellite radio receivers, but they usually are at much higher frequencies (in the megahertz range). This is true because the Earth's ionosphere (a zone of ionized gases with a base at about 60 km) strongly refracts or attenuates radio emissions at frequencies less than ~5 MHz). The exact frequency at which radio wave transmission through the ionosphere occurs depends on the density of the ionosphere, which in turn depends on a number of factors including the time of day and solar activity. It is very rare for emissions as low as a few kilohertz to propagate through the ionosphere. These emissions are referred to as very low frequency (VLF) and, in the case observed on the wave file, are in the “whistler mode“. One way that such low frequencies can propagate through the ionosphere is for the radio emission to travel nearly parallel to the lines of force of the Earth's magnetic field. For this special case, strong wave attenuation can be avoided.“ “It turns out that at the time of the observations on the wave file, the Polar spacecraft was traveling almost parallel to the magnetic field lines of force, thus providing a perfect opportunity for “hearing“ such low frequency emissions. Using a model, we tracked the magnetic field line from the spacecraft back down to the Earth to determine a probable source of the radio emissions. This turns out to be at about 81.8 degrees N latitude and 106.1 degrees E longitude. Consulting a map, this position is near the northern coast of Russia or in the nearby Arctic ocean. Most commercial radio transmitters operate at much higher frequencies than the emissions seen on the wave file. It is possible that the Polar spacecraft plasma wave instrument was detecting transmissions intended for ship-to-ship communication (submarines?) or other short-range communication.“ The originally-released audio file is available at For more examples of space audio without the unnecessarily creative interpretations, see my “Space Audio“ channel:
