New York Botanical Garden
The Galle crater is a Martian crater that happens to look like a smiley face, due to the position of a curved mountain range.
Someone made a good point about our previous post about carbon dioxide melting on Mars. At normal pressure, or the very low atmospheric pressure on Mars (less than 1% of the average at sea level on Earth), dry ice does not melt into liquid. Instead, it sublimes. Sublimation is a word for the phase transition where a solid bypasses liquid entirely and becomes gas. This is what gives the familiar smoke effect you get when you expose dry ice to air. You would need a pressure of over 5 atmospheres, that is five times the pressure at sea level on Earth, or about a thousand times the average pressure on Mars, to create liquid carbon dioxide. Sublimation also occurs to a certain extent to water ice on Earth.
The point at which dry ice sublimates at normal pressure is -56 celsius, which means when the temperature goes below this, the opposite transition, from gas to solid, which is called deposition, occurs. Thus “melts” was not the right word to use in the previous post. This also gives a measure of just what spring on Mars means: the dry ice cover starts melting, sorry, sublimating when the temperature goes above -56.4 C or -69.5 F. Talk about a chilly spring!
The atmosphere on Mars is about 96% carbon dioxide. About 0.1% is oxygen. For comparison, Earth’s atmosphere is about 78% nitrogen and about 21% oxygen.
The somewhat surprising fact, at least to me, that there’s only 21% oxygen in the atmosphere lead to the invention of carbogen, a mixture of oxygen and carbon dioxide. This mixture can be used to simulate the feeling of suffocation without actually suffocating, as the brain does not monitor the oxygen levels in the blood, but rather responds as if you can’t breathe if the blood carbon dioxide levels go too high.