There are juicier planets in the Solar System, but to get started with the art of terraforming, the Moon will be the easiest. The Moon has a little bit of water too (water is heavy, one better find it where one intends to settle). At its densest (around 3.5 billion years ago), the Moon’s atmosphere exerted a pressure of about 1 kilopascal… 50% more than the present Martian atmosphere! For reference, pressure at sea level on Earth is around 100 kilopascal. Martian atmospheric pressure is only .6 kilopascal, corresponding to pressure on Earth at 32 kilometers elevation… plenty enough for areobraking, but not enough to prevent lungs from boiling out.
The extinct Lunar atmosphere originated from Lunar volcanism. That was announced by NASA in 2017, from an analysis of Apollo rocks… Lunar volcanism produced a transient atmosphere around the ancient Moon, Debra H. Needham, David A. Kring.
It is to be noted that the Lunar atmosphere was generated for hundreds of millions of years and took 70 million years to dissipate after the final volcanic activity 3.5 billion years ago. So it is even imaginable that life got started on the Moon (as it is likely for Mars, and possible for Venus)…
The problem with life in the universe is that conditions are so unstable, and life takes so long to evolve into advanced forms. Life got nearly eliminated several times when Earth underwent the “Snowball Earth” episodes, caused by the dramatic drop in GreenHouse Gases due to switching from a GHG reductive atmosphere to one full of oxygen… a disastrous progress that life itself had caused…
The Great Oxygenation Event removed atmospheric methane through oxidation. As the solar irradiance was significantly weaker at the time, Earth’s biosphere may have relied on methane, a much more powerful greenhouse gas than CO2, to maintain surface temperatures above freezing. That may have been 2.25 billion years ago, but there were more, the most recent global glaciation, with the Equator as iced up as Antarctica, may have been around 635 million years ago. (How many Snowballs and how frozen is an ongoing debate…)
This is, by the way, how sushi fish is prepared: a hard freeze for a few hours kills all life in the raw fish, including various parasites… So Earth’s life was lucky to escape those snowball episodes, when glaciers were found at sea level, under the equator (CO2 from volcanoes re-establish enough of a greenhouse later..)
It took more than 4 billion years for life on Earth to generate a sentient civilization. Logically, just from the Snowball events, one can assume that there is a near 100% probability of extinction in two billion years. That’s probably not pessimistic enough: the Lunar volcanism was caused by heavy bombardment… The most frequent stars are Red Dwarves, which are much smaller than the Sun, and thus unstable. The closest star, Proxima Centauri has an Earth Like planet Proxima Centauri b. In a flare of Proxima, the power output of the star was multiplied by eight (8). Flares is how Mars lost most of its atmposphere… (That was learned from Martian orbit).
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Fermi paradox: “Where is everybody?”
…said by Enrico Fermi in the early 1950s at a cafe, to his colleagues. Fermi wanted to point out that there were no extraterrestrials (that there were plenty of extraterrestrials was an old Greco-Roman theory found in Lucan… a poet assassinated by Nero when he was 25…). Anti-fascist Italian Fermi, scientific director of the Manhattan project, got the Nobel for (co-) discovering the neutron with Irene Curie (she didn’t quite clinch the discovery in an earlier paper, being a woman and all that…)
The easiest way to solve the Fermi Paradox is that we should assume: we are it. Hence the interest of settling Mars… says Elon Musk, in these words exactly. Why should we be all the it there is? Because Life is probably frequent in the galaxy… but only at the bacterial stage… sucking methane…
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SpaceX tech will be just enough to settle Mars, after pioneering AI had set up cities on Mars, as I explained. Ultimately, one may want to make Mars more livable for carbon based consciousness, and thus put an atmosphere there. This is called “TERRAFORMING”. Not easy on Mars, easier on the Moon.
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A JUICIER TARGET FOR TERRAFORMING IS THE MOON.
Earth’s Moon is the fifth largest satellite in the Solar System (water rich Ganymede is larger than Mercury). The Moon’s diameter is about 3,500 km, a bit more than a quarter of Earth’s, with the face of the Moon comparable to the width of either Australia, Europe or the US without Alaska. Mars’ diameter is 6,800 kilometers, roughly double the Moon. Hence terraforming Mars will require four times the atmospheric mass. But the Moon has more solar energy available, and the Moon has plenty of readily available oxygen.
An obvious way to put an atmosphere on the Moon is by baking rocks to extract the 40+% of oxygen there. When one looks at the Moon, one looks at 40+% oxygen.
How to get oxygen on Mars? The MOXIE experiment on NASA’s Perseverance rover baked CO2 to separate the O2 from the C… and it worked. So one can convert carbon dioxide from Mars’ atmosphere into oxygen. Future human explorers would have to use this kind of technology to generate oxygen for their habitats.
However, CO2 pressure on Mars is only two-third of 1% of atmospheric pressure on Earth… So it’s basically zero, and there is nothing else. Hence using Martian atmospheric CO2 to generate O2 for the entire planet is not feasible, we would need twenty times more CO2 than the Martian atmosphere contains!
(Vaporizing all the CO2 in Martian polar ice caps would augment the greenhouse effect significantly, but may only at most double the CO2 in the atmosphere…)
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… Whereas on the Moon, there is readily available enough oxygen to make air…
Ilmenite is a common lunar mineral that contains oxygen along with iron and titanium. Ilmenite has the chemical formula FeTiO3. So the percentage of oxygen in Ilmenite is 40% in mass (because three oxygens have 48 H mass, and Titanium is 48 H and Iron is 56 H…). This is just to give an (optimistic) order of ideas… With which we will proceed:
… Lunar surface rock density is roughly three times that of water. So a vaporized layer of 1.7 meter of lunar rock will have the same gaseous pressure as five meters of water, while generating the equivalent in water pressure of two meters of partial O2 (the exact partial O2 pressure on Earth’s surface). Thus vaporizing the first five feet of the entire surface of the Moon would generate the same O2 partial pressure as on Earth presently.
In practice, one may not want to do that: a pure O2 atmosphere may be too flammable, and reducing partial O2 pressure to half of Earth surface, namely the partial O2 pressure at 5,500 meters would be enough. In practice, one could dig a system of holes 4 kilometers deep covering 1/1000 of the Moon’s surface, and generate a livable atmosphere… That means digging a 4 kms deep depression a bit larger than the British isles (with Ireland)…. Esthetically speaking that’s perfectly doable, especially if one filled them with water from (gently) crashed comets, etc…
The deepest depression on the Moon is the South Pole-Aitken Basin. It is one of the largest and oldest impact basins in the solar system. The South Pole-Aitken Basin has a diameter of about 2,500 kilometers (1,550 miles) and reaches a maximum depth of around 13 kilometers (8 miles) below the average lunar surface. It is located near the southern pole of the Moon, encompassing the South Pole and extending toward the lunar equator. The tallest is Mount Huyghens, rising 5.5 kms. So the extent of lowest to highest on the Moon is 18.5 kms, a bit more than twice Earth (which is 8,850 meters at peak of Everest).
Another advantage of putting an O2 atmosphere on the Moon would be to cut ultraviolet light with a layer of O3.
As far as retaining a lunar atmosphere, we are talking millions of years. Indeed…
On the Moon, the escape velocity is approximately 2.38 kilometers per second (km/s) or about 1.48 miles per second (mi/s). In comparison, the escape velocity on Earth is approximately 11.2 km/s (6.95 mi/s).
At room temperature, the root mean square speed of an oxygen molecule in Earth’s atmosphere is approximately 484 m/s. At 127 degrees Celsius, the maximum Moon temperature, the average root mean square speed of oxygen molecules is roughly 517 m/s. Ar -173 degrees Celsius, the Moon’s coldest temperature, it’s less than 220 m/s…) Hydrogen can be expected to go at 1932 m/s… Water molecule at 625 m/s…. In any case, not enough speed for any of these molecules to escape…
The location of the Moon provides much quasi free energy from solar cells. Those could be made on the Moon in automated factories…
Moon terraforming is an obvious easy picking. All the Moon needs is an atmosphere. Notice too that the Moon is 38 million square kilometers, that is slightly larger than the USA plus China plus Russia, or larger than the USA plus China, plus Canada, plus Australia…
Lunatics such as yours truly are already all excited…
Humanize The Moon!
Patrice Ayme