Presence of Water on Mars
Mars is the planet nearest to Earth that we are most likely to explore and send manned missions to. It also is the planet that we have the best chance of finding life on. For both these things water is needed so exploration of Mars by space probes has concentrated on looking for water.
Humans have searched for evidence of water on Mars for many years. In 1895
American astronomer Percival Lowell thought that he had seen canals on the surface of Mars. These were disproved as tricks of the eye. Spacecraft in the 1960’s and 1970’s reported that Mars was very dry. However, spacecraft in the 1970’s to the 1990’s started to report evidence of water, either past or present. The atmosphere of Mars is very thin, only 1% of the Earth’s atmosphere, so it cannot hold water droplets for rain. But plenty of evidence was found of huge, catastrophic floods, such as channels on the surface, sedimentary layers and lake beds, even though these could have other explanations such as lava flows.
Scientists have used their knowledge on how water shaped features appear on
Earth to examine similar features on Mars and deduce the past or recent presence of water. Also geologists know which minerals are formed by water on Earth, so if these are found on Mars they indicate that water was once present.
Also important in interpreting discoveries of water on Mars is the “triple point of water”. This is “the combination of pressure (6.1 millibars) and temperature (0.01 o C) at which water can exist simultaneously as a liquid, solid or gas. http://science.nasa.gov/headlines/y2000/ast29jun_1m.htm
The atmospheric pressure on Mars means that water is very close to the triple point of water. This means that it is very difficult for water to be liquid, rather than ice or water vapour. Liquid water cannot exist below 6.1 millibars, which is about the atmospheric pressure on Mars. Water as ice or water vapour is not useful
Humans have searched for evidence of water on Mars for many years. In 1895
American astronomer Percival Lowell thought that he had seen canals on the surface of Mars. These were disproved as tricks of the eye. Spacecraft in the 1960’s and 1970’s reported that Mars was very dry. However, spacecraft in the 1970’s to the 1990’s started to report evidence of water, either past or present. The atmosphere of Mars is very thin, only 1% of the Earth’s atmosphere, so it cannot hold water droplets for rain. But plenty of evidence was found of huge, catastrophic floods, such as channels on the surface, sedimentary layers and lake beds, even though these could have other explanations such as lava flows.
Scientists have used their knowledge on how water shaped features appear on
Earth to examine similar features on Mars and deduce the past or recent presence of water. Also geologists know which minerals are formed by water on Earth, so if these are found on Mars they indicate that water was once present.
Also important in interpreting discoveries of water on Mars is the “triple point of water”. This is “the combination of pressure (6.1 millibars) and temperature (0.01 o C) at which water can exist simultaneously as a liquid, solid or gas. http://science.nasa.gov/headlines/y2000/ast29jun_1m.htm
The atmospheric pressure on Mars means that water is very close to the triple point of water. This means that it is very difficult for water to be liquid, rather than ice or water vapour. Liquid water cannot exist below 6.1 millibars, which is about the atmospheric pressure on Mars. Water as ice or water vapour is not useful