If you follow news from around the solar system, you may have heard that Mars is losing what little atmosphere it has because it has no magnetosphere to “rescue” its atmosphere from being stripped away from the solar wind. Before you feel smug about being nice and safe with a comfy blanket of atmosphere held in place by Earth’s magnetosphere, though, keep in mind that about 90 metric tons of atmosphere every day.
There’s no need to panic quite yet, though. This is 90 metric tons out of about 5 quadrillion tons of atmosphere and this is only happening because some particles near the top of the atmosphere are moving so fast that they escape Earth’s gravity. Think of it as watching little wafts of steam evaporating away from a puddle after it just rained in the middle of a hot Florida day, if you like. You know it’s still going to be a bit before that puddle is dried up. This happens because some water molecules at the surface absorb enough heat to vibrate its way to freedom as vapor that still lingers in the atmosphere until the next time it rains. Earth’s magnetic field is simply doing the same thing to charged particles at the top of Earth’s atmosphere, and then capturing those particles in the magnetosphere, where they linger until they are blown away by the solar wind.
Window Of Opportunity for the Moon to Collect Oxygen
For most of each lunar month, the Moon is bombarded by the same solar wind, which can hamper its ability to collect slower moving particles like those being accelerated away from Earth’s atmosphere. However, the Moon moves into the magnetosphere for five days out of every month, which gives it time to accumulate elements like oxygen that have escaped Earth. It’s estimated that the Moon may have gathered 4×1024 atoms of oxygen in the past 2.4 billion years this way.
Japan’s lunar probe, Kaguya, was the first to collect data suggesting this phenomenon. Scientists noticed a difference in the oxygen ions that hit one of Kaguya’s sensors during the five days that the Moon dives into Earth’s magnetosphere. The ions move at a slower speed and may also be identical to the oxygen-17 and oxygen-18 isotopes that baffled scientists when they were discovered in higher-than-normal concentrations in lunar dust samples brought back by Apollo astronauts. A slightly different isotope, oxygen-16, is believed to be more common than either of these types of isotopes.
A U.K. cosmochemist named Mahesh Anand said of it, “No one has ever had a convincing explanation for how those anomalies could occur in lunar soil.” However, scientists are starting to get a better handle on the matter using data from Kaguya and scientific satellites operated by the European Space Agency. By comparing the data, scientists can improve their models of atmospheric chemistry taking place in the upper atmosphere. This includes the processes by which oxygen-17 and oxygen-18 may be transferred from Earth to the Moon.
Can This Provide Enough Oxygen To Support Colonization?
On the surface, there would appear that the sheer number of oxygen atoms on the Moon could support life. Anyway, it would be only fair considering that the Moon appears to be stealing oxygen from Earth with help from the upper atmosphere’s interactions with the magnetosphere. However, keep in mind that most of the oxygen has been mixed in and probably chemically bound to the dust on the Moon. It would take special equipment that is likely to be an energy hog to extract that oxygen in a usable form. That means any oxygen used by future lunar colonists are likely to either be brought with them or produced using other methods.
Until then, it’s unlikely that we’ll run out of oxygen here on Earth anytime soon. Because Earth has a magnetosphere, it’s actually losing less of its atmosphere every day than Mars is. That means you can breathe more easily knowing that you won’t run out of air to breathe.