Published on January 20th, 2013 | by Scott1
So why doesn’t Mars have an atmosphere like Earth’s?
Tonight on Google+ I was made aware of an article from Popular Science that was published on their site almost two years ago, speaking of terraforming Mars and what we need to do in order to make that possible.
+ Adding carbon dioxide to Mars’s atmosphere won’t warm it more than it already is.
+ There’s more to keeping an atmosphere than what it’s made up of.
+ Charged particles from the sun (Solar Wind) will irradiate and strip a planet of gas from its atmosphere.
+ Earth is protected from this Solar Wind due to active geology which generates a magnetic field.
+ Mars’s geology is not active, so no magnetic field is generated to protect its atmosphere from being stripped away.
The article focuses how Mars is very cold, compared to Earth, and that in order to make our reddish neighbor more “Earth-Like”, its temperature would need to increase by some unknown method. The idea suggested is of adding fluorocarbons to the atmosphere in order to absorb more of the sun’s rays in an attempt to create a greenhouse effect.
Though it’s very true that Mars is much colder than Earth and that the greenhouse effect is an effective method of warming up a planet (see Venus), there’s a bit of an issue of focusing just on this. The reason why we, and Venus, have a greenhouse effect is that the Sun’s photons go through our atmosphere, which heat the ground, which then emits infrared (black body) radiation back up. Greenhouse gasses (Water vapor, CO2, Methane, Nitrous Oxide and Ozone) then absorb this infrared radiation (heat) and then re-emitted, heating the upper atmosphere and the Earth again.
Mars’s atmosphere is already ~95% Carbon Dioxide, meaning there really isn’t much room for more greenhouse gasses to influence the temperature of the surface of Mars in order to soften the soil, etc. Another big issue is that the amount of matter in the atmosphere is about 0.6% that of Earth’s, so there are fewer molecules for this infrared radiation to even come in contact with, let alone heat back up. So why is there so little atmosphere on Mars?
A different wind blowing away the atmosphere
There’s a very important reason why Mars has so very little atmosphere right now, and has very little to do with its composition. The Sun releases a stream of charged particles (mostly electrons and protons) out into space all the time. They bombard anything that comes into its path, which means that if there’s nothing there to protect it, it’s getting blasted hard. We’re quite fortunate here on Earth because of one fantastic thing keeping our atmosphere safe, our magnetic field. You see, under the surface of the Earth, many intense activities are happening which generate an invisible (to human eyes) field which protects our entire planet. Friction is causing a magnetic field to generate around our pale blue dot in the cosmos, so that when this solar wind is pointed at our direction, it’s absorbed by it instead of passing right on through. Have you ever seen the Aurora Borealis or Aurora Australis? That’s watching the stream of particles slam into the magnetic field and channel down to the magnetic north and south poles of Earth.
So what does that have to do with Mars? Well, I really hate to be the bearer of bad news, but Mars is geologically dead. There’s no active plate tectonics on the red planet, meaning there’s no friction under the surface to generate a magnetic field. Without this magnetic field, the atmosphere that was on Mars, is no longer there resulting with the solar wind literally blowing its atmosphere out into space. The first time I realized this, it made me appreciate the earthquakes I have to deal with here in Los Angeles. Our geology is active, which means we’re extremely fortunate to live on a planet which has this magnetism protecting it from the violence being ejected from the sun.
Hope this helps shed some insight on how important geology is when it comes to having an atmosphere. Next time you see a photo of a volcano or feel a rumble of an earthquake, take it as a reminder that we also have an “invisible shield” which is also generated with these to protect us from the Sun’s radiation.
Have a great Science Sunday!
The article in question can be found here.
Image Source: NASA – http://www.nasa.gov/mission_pages/mars/news/maven_20080915.html