Atmosphere vs. Atmosphere

Links for different Landing Methods Viking (1976) 4:01 Pathfinder (1997) 2:43 Spirit/Opportunity (2004) 4:41 Phoenix (2008) 2:44 Curiosity (2012) 5:12 LDSD “Flying Saucer” Idea (2014) 2:08

Atmosphere of Earth SubstanceAbundance (%)Notes Nitrogen78.08Mostly inert Oxygen20.94Pretty important Argon0.93Inert Water vaporVariable (~1%)Greenhouse gas Carbon dioxide0.040Greenhouse gas Neon0.0018Inert Helium0.0005Inert Methane0.0002Potent greenhouse gas Surface pressure: ~1014 millibars

Atmosphere of Mars SubstanceAbundance (%)Notes Carbon dioxide95.32It’s what plants crave! Nitrogen2.7So much less than Earth. Argon1.6Inert. Oxygen0.13Frowny face. Carbon monoxide0.08Deadly at higher concentrations. Water No, you can’t go to the school store. Surface pressure: ~6.6 millibars

Where’d it go? In July 2013, NASA reported that its Curiosity rover had found evidence that Mars lost the bulk of its atmosphere in a catastrophic event 4 billion years ago. For you chemistry kids, the ratio of two isotopes of argon on Mars is very different to that on Earth, suggesting that some unpleasant event changed the original composition of Mars’ atmosphere. As with every other major planetary event, it was either a giant impact or volcanic activity. We don’t know yet.

Where’d it go? Of course, Mars also lacks a planetary magnetic field, and that is the traditional explanation for the thin atmosphere. Outgassing from the Martian interior is in equilibrium with the thinning of the atmosphere by the solar wind.

Earth Magnetic Field vs Mars/Venus An artist's impression of the magnetic fields of Venus, Earth and Mars interacting with charged particles streaming from the sun. Earth's magnetic field protects it from these atmosphere-stripping particles

Solar Wind on Mars Earth has a fairly strong magnetic field (compared to other planets. Solar wind is charged particles (mostly protons) that escape the Sun’s gravity and travels out into space in all directions. These particles are a form of radiation which can cause damage to eyes and skin and cause cancer. Since Mars has no magnetic field, humans on Mars would need shielding from the radiation in order to live safely. (For building, spacesuits, vehicles, etc.)

Solar Radiation Is energy radiated from the sun in the form of electromagnetic waves, including visible and ultraviolet light and infrared radiation.

Earth’s atmosphere protects us from UV radiation (solar radiation))

Radiation on our journey to Mars radiation-protection-plastic.html radiation-protection-plastic.html