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Sep 2, 2012

Planetary Space Exploration: 50 Years

Back side of Moon
I was born in 1959, the year when seven Project Mercury astronauts were selected and construction of the Saturn rocket launch facilities began at Cape Canaveral. The obvious first target for manned space travel was the Moon, but scientists had their sights set on the planets. The Explorer 6 satellite transmitted television images of the Earth and began the study of Earth's atmosphere and cloud cover. LUNIK III returned images of the back side of the Moon. In exodemic stories I frequently pretend that the Huaoshy long ago established a base on the far side of the Moon.

Where is the carbon dioxide? You are standing on it.
Carbon dioxide. In 1962 the Mariner 2 probe went past Venus and its instruments confirmed the thick CO2 atmosphere, lack of a magnetic field and the very high surface temperature for that planet. The major component of the atmospheres of both Venus and Mars is carbon dioxide: 96% and 95% of the their atmospheres, respectively. Earth has a much lower fraction of its atmosphere as carbon dioxide (less than 0.1%), but even that much is important for our global temperature. Where is all the carbon dioxide on Earth? During the long history of the Earth atmospheric carbon dioxide has dissolved in seawater and been deposited in carbonate-containing rock such as limestone.

Due to Earth's active plate tectonics, subducted sedimentary rock can release the carbon dixode back to the atmosphere during volcanic activity. Keeping  reasonable balance between carbon dioxide deposition and out gassing is important for a stable biosphere. In my fan fiction X-Files/Star Trek crossover story (X-Seven) I included an Interventionist plot designed to speed carbon dioxide trapping in the oceans as a solution to anthropogenic global warming.

Water. Venus is hot and dry (although science fiction writers like Campbell wished that it might be wet). The combined effects of a location close to the sun and lack of a magnetic field probably means that for the past couple of billion years atmospheric water molecules were split apart and hydrogen was blown away by the solar wind.

Venus
Mars
This left Venus as a desiccated green house smothered under about 100 times more atmosphere than Earth, most of it heat-trapping carbon dioxide, resulting in surface temperatures above 800 °F.

At the other extreme, Mars is cold but it apparently had liquid water long ago. Antarctica probably has about 1000 times more water than the south polar ice cap of Mars.

In science fiction stories it is fun to imagine future cultures for which there are adequate technological resources for serious terraforming of planets. Mars is a better candidate for terraforming, but it is fun to imagine that it might become possible to float "cloud cities" in the thick atmosphere of Venus.

Polar Mercury base
Mercury is even closer to the sun than Venus and it is small, with little gravity to hold onto an atmosphere. In 1974 Mariner 10 flew by Mercury and confirmed that the magnetic field is only about 1% that of Earth's and there is essentially no atmosphere.

Strata to be studied by Curiosity rover
However, there are deep polar craters that might contain frozen water, making it possible that people might one day colonize parts of Mercury.

Right now the Curiosity rover is on its way to explore what appear to be sedimentary rock layers on Mars. It will be interesting to see if this mission can find evidence for carbonates or other carbon dioxide-based deposits, as was suggested by data from the Spirit rover in the Columbia Hills. Related Reading.

Future Mars
Ancient Mars
In The Search for Kalid I imagined that Mars had become the target for an active terraforming effort. Exode will end with the crew of a Buld spaceship taking up residence on Mars and initiating a terraforming process.

The Buld have access to some sophisticated hierion-based technology. In particular, the hierion-powered engine of their spaceship has taken them all the way from the galactic core to Earth. With a source of essentially unlimited energy, it would be possible to melt the ice caps of Mars and start warming the planet.

Oxygen. Another technology available to the Buld is nanotechnology. It is easy to imagine that a sophisticated nanotechnology would allow for efficient conversion of carbon dioxide to oxygen and carbon compounds. It might be possible for self-replicating nanites to scavenge the atomic constituents from the lithosphere that would be needed to fully produce an Earth-like atmosphere on Mars. With hierion technology it might also be possible to harvest vast quantities of water, ammonia and methane from Titan and deliver it to Mars.

Nitrogen. The most prevalent atom in Earth's atmosphere is nitrogen. Nitrogen is the 7th most common element in the Solar System but it is about ten times less abundant than oxygen. During the formation of the terrestrial planets much of the nitrogen was lost by solar heating and blown away by the solar wind. Nitrogen is much less reactive than oxygen during planet formation and it is lost much more easily from forming planets than is oxygen. Nitrogen is probably present at relatively low abundance in the lithosphere of Mars (maybe about 10,000 times less than oxygen). Even so, it might be possible for swarms of nanites to mine and release enough nitrogen gas to provide Mars with an Earth-like concentration of atmospheric nitrogen (related reading). If energy is not limiting in a hierion-based civilization, it might be convenient to mine the atmosphere of Venus for both nitrogen and carbon dioxide.

Instant atmosphere!
Time. Given a hierion-based source of limitless energy and swarms of self-replicating nanites, how long might it take to provide Mars with an Earth-like atmosphere?

In the movie Total Recall an alien device is able to almost instantly manufacture an atmosphere for Mars.  Ah, the wonders of Hollywood.

In Hollywood anything is possible...

Magnetic field. Even if it were possible to provide Mars with an Earth-like atmosphere, it would also be nice to provide the planet with a protective magnetic field. In Exode, The Buld spaceship arriving at Mars first travels through the galaxy for thousands of years at a speed slightly below the speed of light. I assume that the hierion-based engine of the spaceship is able to generate a protective magnetic field and keep the passengers safe from cosmic rays. Hopefully hierions will also provide a way to wrap Mars in a protective magnetic field.

Exploration of the Solar System during the past 50 years has provided us with an increasingly detailed understanding of the planets. Science fiction stories need to continually adjust to the latest facts about other worlds. Many readers of science fiction are well informed about planetary science and upset when SciFi stories don't depict realistic conditions on familiar worlds like Mars.

I expect the next 50 years to be dominated by the study of extrasolar planets.

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