Tuesday, November 22, 2011
Wired has published an article today that I wish everyone interested in space would read at least once, if only to realize what a difficult destination Mars is to land on. The problem with Mars is that it looks extremely friendly and familiar - valleys, channels, ice caps, mountains, a 26-hour day, seasons and all the rest. But what's the problem? The atmosphere. The atmosphere is thick enough that one requires a heat shield to land and wind and weather must be taken into account when using retrorockets, but thin enough that parachutes don't provide that much of a decrease in velocity when landing. As a result, the upcoming Mars Science Laboratory represents more or less the limit of mass we're able to land there.
Oh, and don't forget the absolutely terrible time between launch windows, the worst of any major body in the Solar System. Mars clocks in at 2.1 years, while Venus is 1.6 years. All the other bodies except the moon (since it orbits us) are approximately a year and a bit. Mercury is also an exception here because of how difficult it is to match one's velocity with it as it zips around the sun, making it quite a difficult destination to reach.
The best example for a body nearly opposite of Mars is the moon Titan. In spite of the great distance from us and our complete lack of experience in landing anything there, the Huygens orbiter had no problem at all carrying out a soft landing on the surface and transmitting for some time after too. No surprise considering that Titan has an atmosphere that is both thicker than ours and a much weaker gravity.
Venus is another good example of a body with a nearly ideal atmosphere...as long as one stays up in the clouds, that is. A probe of just about any mass and complexity can be sent there as long as it is capable of staying afloat and resistant to corrosion. A solar flyer or balloon for example. Landings are also fairly easy; it's just the harsh conditions on the surface that limit the length of time a lander can function.
So where should we explore? Easy: first the moon, asteroids (minor planets) next. The best minor planet to explore may be 24 Themis, an asteroid in the asteroid belt covered in ice that is 200 km in diameter, giving a total surface area greater than Bulgaria.
One other option, if we are mostly concerned with terraforming, is to consider starting small: instead of trying to terraform an entire planet the size of Mars, find a suitable asteroid (perhaps some 20 km or so in diameter with enough gravity that one does not break orbit by jumping too high), and paraterraform it. In other words, build a roof across more or less the whole surface, pressurize the inside and live there. An asteroid with a diameter of 40 km would have a surface area roughly equivalent to Brunei (or Luxembourg times two), about 30,000 times less surface area than Mars.
I am firmly convinced that the only way to break out of this moon or Mars moon or Mars moon or Mars loop we seem to be in is to realize that 1) the moon is going to be colonized by other countries in the next decade or so even if the US is not interested and 2) there are *way* more destinations nearby than just the planets everyone knows. A body does not officially need to be deemed a planet in order for us to settle it, to make it our second home.