- Speaker: Wesley Andres Watters
- Date: Saturday 3 May 2014
- Duration: 45min
- Location: Within Observatory, Wellesley College, MA
Professor Wesley Andres Watters is a planetary scientist who studies the planet Mars while teaching courses about the geology and climates of rocky and icy worlds.
Earth's atmosphere has good conditions to live. Temperatures are not extremes thanks to the atmosphere and the greenhouse effect.
Cloud maps show a lot of clouds along the Equator. When looking at infrared images of the Earth, heat is mainly emitted by two horizontal bands just above and just under the Equator. This is explained by water currents. Water is absorbing a lot of light. In deserts, everything is dry, there is no water in the atmosphere to absorb the infrareds.
The Early Earth (name given to the Earth's first billion years) had a closer Moon than nowadays, it was mainly an ocean with tiny volcanic islands, no continents. We think it was a CO2-rich atmospehre, also composed of ammonia and methane. The rotation period of the Early Earth was 3 to 5 hours, so days were shorter.
The Snowball Earth is an hypothesis that posits that the Earth was entirely covered in ice (650 million years ago). This is different from the frosts that happened frequently but did not cover the entire planet.
Ground temperature on the Moon varies from -150°C to +150°C because there is barely no atmosphere. Such as Mercure, a lot of things constantly hit the surface of the Moon, which contributes to its very hostile environment. There is no air, a human body would suffocate. There is no pressure either, so it would critically expand. However, unlike in the movies, a human body would not instantly freeze but instead cool off slowly due to the vacuum.
The atmosphere on Venus is opaque, the surface of the planet cannot be seen. It is primarily composed of CO2 (96-97%). There is twice as much solar radiation compared to the Earth but the clouds reflect 80% of this radiation. The greenhouse effect is very strong so the temperature is much higher, even with all these radiations reflected.
We do not have evidence of a continuous volcanic activity. Sulfuric acid decomposes so it is not the source of the clouds. However, one theory posits that volcans are still in activity and produce these clouds.
There is some atmosphere on Mars protecting the surface from solar winds. This would protect a body's DNA and tissues. As opposed to Venus, its atmosphere is transparent. There are clouds as well as traces of water in the sky of Mars. The average temperature is -60°C and the average surface pressure is about 0.6% of Earth's atmospheric pressure. Its atmosphere is mainly composed of CO2 (95%).
Mars has the tallest volcano of the solar system, Olympus Mons.
We think that there were large amounts of water on Mars and that they desiccated over time, about 3 billion years ago.
There are enormous oscillations on the rotation axis of Mars, raising the pressure on the surface, as well as the temperature.
The weather conditions are not catastrophic but the planet is often subject to global dust storms. They tend to start during Marsian summer. Its elliptical orbit changes a lot the solar radiation received by the planet (by about 40%), which creates these dust storms that last several months. In only a month, the atmosphere gets very dark.
Mars would be the least technical challenge to establish human colonies.
Titan is one of the moons of Saturn and the most exciting world we have explored in recent years. It is larger than the Moon but smaller than the Earth. A day on Titan is longer than a year on Earth.
Titan is mostly composed of water ice and rocky material. Its average temperature is -180°C. The average pressure is 50% of Earth's pressure, one would feel heavy. However, the gravity is lower, humans could fly.
As opposed to Venus and its greenhouse effet, infrared light is getting through while direct light does not. We call this the anti-greenhouse effect. Titan's atmosphere contains a lot of methane and we can find seas of methane there. Its atmosphere is far more extended than Earth's atmosphere due to its low gravity.
Titan's characteristics look like Earth's (due to the presence of oceans, waves, rain, ...) except that methane replaces water.