never mind the bizarre theories that have put aliens on the moon constructing creepy obelisks and even inside to pilot it like a spaceship—new revelations about its vanished magnetic field may shed light on how other moons could potentially host alien life forms.
While the moon now has nothing but a ghost of what was once a magnetic field, a new study has found that its magnetic field must have lasted a billion years longer than what scientists previously estimated. This extended shelf life could mean that magnetic fields on distant celestial bodies may be able to survive long enough to support some sort of extraterrestrial life.
Whether anything ever crawled around on the moon itself is a mystery, but science has been able to find out approximately how strong its dead magnetic field used to be by using moon rocks brought back to Earth by Apollo astronauts. The rocks are relics of a period between 3.56 and 4.25 billion years ago, when the moon’s magnetic field could have been anywhere from 20 to 110 microtesla (in comparison to Earth’s 50). Sometime around 3.19 billion years ago, the strength of the lunar magnetic field plunged to under 4 microteslas, and the question of what happened after that and before it dissipated completely remains unanswered.
Greater insight into what the magnetic field of the moon was like when it actually existed could tell us more about how those of alien moons and planets influence their potential for habitability. Earth’s magnetic field shields our planet from getting radiation-bombed by the sun, as Mars did when its own was ruthlessly stripped away by stellar winds to turn it from a planet that is thought to have once been running with rivers into a dry, dusty wasteland.
"Magnetic fields can shield planets from stellar winds which can strip atmospheres of water, which is important for planetary habitability," said lunar geophysicist Sonia Tikoo, who led a study recently published in Science Advances.
An Apollo 15 moon rock, sample 15498, was tested by Tikkoo and her colleagues for what it could reveal about the past. Moon rocks have preserved evidence of the existence and strength of the moon’s ancient magnetic field through thousands of metallic micrograins that aligned with its force as they cooled from a molten state. 15498 is one of the rare ones that formed after volcanism on the moon, and with it, igneous rock formation sputtered to death 3 billion years ago. This one was found to have formed from an intense cosmic impact around 1 to 2.5 billion years ago.
Sample 15498’s magnetic properties were first gauged by a supersensitive magnetometer before it was exposed to an artificial magnetic field in the lab. The rock was then heated to be as close as possible to the extreme temperatures it emerged from, about 1,436 degrees Fahrenheit. How magnetized the rock gets is compared to the natural magnetic field previously measured to determine what the strength of the lunar magnetic field was when it formed. The rock revealed that there was still the vestige of a magnetic field with a strength of 5 microteslas from 1 to 2.5 billion years ago.
The reason the magnetic field held on for so long is thought to be a dynamo much like Earth’s liquid metal core (which fuels our own magnetic field). There are several theories as to how the lunar dynamo could have lasted for billions of years, but it is still an unsolved mystery.
What was once a liquid metallic core (that glowing red thing that looks like the Eye of Sauron) is thought to be what made the lunar magnetic field last a billion years longer than previously thought.
So what does all this say about aliens?
“Even small planetary bodies can generate long-lived magnetic fields operating on billion-year timescales, so it is possible that small exoplanets or exomoons might be able to preserve water on timescales long enough to permit life to develop,” said Tikoo.
Don’t be surprised if the first sign of extraterrestrial life emerges from an exomoon.
