Sunday, September 18, 2005
The Big Solar Flares Of 2005 And Human Settlement Of Space.
A Coronal Mass Ejection hit the Earth on September 7th producing some auroras. According to NASA, this month's solar activity "[w]ith the exception of brief radio blackouts, the flares have had little effect on Earth, although the NOAA Space Environment Center warns that as the spot continues to rotate toward Earth, agencies impacted by space weather storms may experience disruptions over the next two weeks. These include spacecraft operators, electric power systems, high frequency communications, and low-frequency navigation systems."
The JPL Rover home page (here) has no information whether the flare activity has had any effect on Spirit or Opportunity. Nor do Mars Odyssey, Mars Global Surveyor or Mars Reconnaissance Orbiter. (Here, here, and here.)
Things have not always gone so well.
According to this NASA report from Summer 2004 (here) "the MARIE instrument on the Mars Odyssey spacecraft was not as lucky. Ironically its task was to better understand solar radiation on Mars. It was able to make observations up until a powerful Oct. 28 CME overheated a power converter." And this report (here) describes the radiation risks to astronauts on the Moon without an atmosphere or magnetic field to protect them from solar flare activity. The bottom line is that solar flare activity is a danger to people and machines in space beyond the protection of Earth's magnetic field.
Mars has no global magnetic field and a very thin atmosphere. Humans and machines there are at risk from the kind of solar activity that does little more than cause annoying radio blackouts and beautiful auroras here on Earth. This is often described as not being a show stopper because it's an engineering problem that is solvable: for instance, by building Mars homes underground, using water as a radiation shield, generating magnetic fields to protect ships and bases, or even building spaceships with plastic (here).
Advocates of human spaceflight often say that we have to settle other planets, particularly Mars, because we don't want to leave all our eggs in one basket on Earth. For instance, if an asteroid hit the Earth, civilization would die if there were no colonies on other planets.
Yet a glance at Mars, for example, reveals a planet that is pocked with impact craters all over its surface. There's no big moon in the sky with a gravity well that could lure passing asteroids to strike it rather than Mars. Not coincidentally, Mars orbits fourth from the Sun, right next to the Asteroid Belt. Indeed, the moons of Mars are believed to be captured asteroids. Mars has no planet-wide magnetic field for protection from solar radiation. The atmosphere is 1/100th as dense as Earth's and it has almost no oxygen. The ground is regolith not soil and is covered with peroxides and dust. The winds of Mars, even with the thin atmosphere, whip up planet-wide dust storms that can last for a month. The dust is probably as sharp as the dust of the Moon because of the lack of moisture. The dust of the Moon is so sharp that it shredded the gloves of astronauts who visited there. The gravity is only 38 percent of Earth's.
Yet Mars is often described as the best location for settlement because it is the most Earth-like planet in the solar system. A better term would be "least inhospitable Earth-type" rather than "most Earth-like."
Mars and the other worlds of this solar system seem like awfully harsh new baskets to put our eggs in. Where would you bet on a global catastrophe occurring first, Earth or Mars?
But it's human destiny to settle the Solar System and I'm all for it. We've spread from Africa to cover the Earth and we are now traveling off planet. Our history of migration tells us it's inevitable that one day we will build colonies then cities and civilizations on the other worlds of the Heliosphere. But the other planets have much harsher environments than the Earth. Life there will be much harder than on Earth and people will have a more tenuous grip on survival. Future space settlers would do well to maintain close relations with Earth, the safest basket of them all for humanity's eggs.