In 1961, astronomer and astrophysicist Frank Drake developed an equation to estimate the number of active extraterrestrial civilizations in the Milky Way galaxy using factors such as rate of star formation, number of planets, length of time intelligent civilizations needed to release detectable signals into space and other obviously speculate but ‘intelligent’ guesses. The now famous Drake Equation, with Drake’s estimates, gave a range from a minimum of 20 to a maximum of 50,000,000. The equation has been debated and refined and has inspired many people to join the Search for Extraterrestrial Intelligence (SETI). Not James Benford. He has developed his own version of the Drake equation to look for signs of extraterrestrial artifacts (SETA) and it tells him we should find them on the Moon. Do lunar astronauts need to start carrying metal detectors?
“The virtue of searching for artifacts is their lingering endurance in space, long after they go dead.”
In a study published in the journal in the journal Astrobiology and reviewed by Space.com, James Benford, a physicist at Microwave Sciences in Lafayette, California, outlines his justifications for SETA over SETI – specifically, that artifacts last far longer the signals, they can be left as static indicators of alien presence and observation by ETs who don’t want to be discovered until after they leave, and they can be found on planets and space bodies that don’t necessarily show signs of life, like the Moon.
“I construct a ratio of a SETA Drake equation for artifacts to the conventional Drake equation so that most terms cancel out. This ratio is a good way to debate the efficacy of SETI versus SETA. The ratio is the product of two terms: one is the ratio of the length of time that probes from extraterrestrial (ET) civilizations could be present in the near-Earth region to the length of time that ET civilizations transmit signals to the Solar System. The second term is the ratio of the respective origin volumes: the volume from which probes can come, which is affected by the long-term passage of stars near the Sun, to the volume of transmitting civilizations.”
Benford thinks SETA is more appealing because it involves an active search, while SETI is more of a passive sit-and-wait-for-a-signal approach. Also, artifacts are a better sign of an advanced intelligence capable of long-distance space travel, whereas we humans are capable of sending signals but not traveling too far or too fast in space. Who wants to find more beings who can only do that?
"You can see Neil Armstrong's footprints on the moon in some photos, but only a handful of these images have been inspected by human eyes. We need to use AI [artificial intelligence] software to look for structures, for signs of artificiality, which could benefit sciences on Earth, such as archaeology."
Benford argues that NASA's Lunar Reconnaissance Orbiter has taken about 2 million photos of the moon since 2009 but they haven’t been analyzed for signs of non-lunar artificiality – artifacts. He also proposes that the solar system could have been visited by ETs from stars that have passed near the Sun -- Scholz's Star came within 0.82 light-years of the sun just 70,000 years ago, and two stars came with 10 light years in the past 10,000 years. ETs from those stars could have sent robotic probes just as we do to Mars and the Moon – probes that can survive for millions of years in those types of environments.
Benford is not the first to propose looking for alien artifacts, but he’s the first to develop an alternative Drake equation for SETA. Searching for alien artifacts, even if it’s just on photographs, beats waiting around for contact or for humans to develop interstellar space travel.
Sorry Dr. Drake!