Exploratour - Life in the Solar System

This is an image of the surface of Mars.
Click on image for full size

Now let's discuss what we know today about the planets in the solar system. Mercury is the closest planet to the Sun, and it orbits the Sun in a variation of a condition called "tidal lock". Tidal lock usually means that the planet always has the same face toward the Sun. Mercury rotates about 1 1/2 times the speed at which it goes around the Sun, so it keeps the same face toward the Sun for a long time.

Mercury also has little atmosphere. Scientists have detected the presence of atmospheric molecules, but there are so few molecules that it is hard to call it an atmsophere. With so little atmosphere, there cannot be a greenhouse effect to keep the temperatures warm and equally distributed between the side of Mercury which faces the Sun and the side of Mercury which faces away from the Sun. The side of Mercury which faces away from the Sun will be very cold because it is virtually directly exposed to space. The side of Mercury which faces the Sun will be very hot! This means that life forms would have to survive both the extreme heat as well as the extreme cold. That is hard to do.

Such life forms would also have to survive the extreme radiation (another name for "charged particles") found in the environment near the Sun. Such radiation has enough energy to break apart long molecules required by life, so it would be difficult for life to get started on Mercury. The magnetosphere of the Earth protects the Earth from these particles streaming away from the Sun. Mercury has a magnetosphere, but is it much smaller than the Earth's, and Mercury is much closer to the Sun.

You can leave the tour and read more about the greenhouse effect by leaving this tour and linking to the greenhouse effect at the bottom of this page. Or read about terrestrial bacteria called Archaea which can survive extreme heat.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA