Is there really water on Mars?

For the world, 2008 is a year in which the amount of water on the earth suddenly increased and decreased. When drought and flood occupied everyone's mind, some people turned their eyes to reports thousands of miles away, because the Phoenix Mars lander landed on our sister planet.

/kloc-in the 0/9th century, when astronomers caught a glimpse of the traces of canals on the surface of Mars, people's imagination of Mars became active. Scientists are thinking about the possibility of life on this red planet. At the same time, artists and visionaries have further expanded this idea. For example, herbert george wells described the imaginary scene of Martians conquering the earth in his book The War of the World from 65438 to 0898. With the passage of time, scientists' discoveries have broken people's expectations one after another, but some questions still exist: Did Mars ever have life? Can its conditions support human migration? Both cases depend on liquid water.

14 after the success of mission to mars, NASA successfully launched the Mars reconnaissance orbiter in 2005, and these problems were still widespread at that time. However, when scientists compared the high-resolution 3D images of Mars taken by the orbiter with those taken by 1999, they found something unusual. In these two shots, bright and deep stripes appeared in the gullies on the surface of Mars. Because mountain torrents can peel off soil and leave new sediments on land, some observers think they have found strong evidence to prove the existence of liquid water on Mars, so Mars has the potential to breed life.

Because life as we know it-even the strangest species-depends on liquid water, scientists believe that liquid water is also a necessity for alien life. Mars has a lot of water, but most of it exists in the form of freezing or steam. For example, the poles of Mars are covered with ice, and solid ice is also distributed on the dunes of craters.

But until the Mars reconnaissance orbiter began to orbit Mars and the Phoenix Mars lander landed on its surface, most people thought that even if there was liquid water on Mars, it would never exist again. The atmosphere and temperature on the surface of Mars make this idea impossible. Mars is extremely dry, and its distance from the sun keeps its temperature at 22 to-124 degrees Fahrenheit (-5.5 to -86.7 degrees Celsius).

However, liquid water on Mars does not need to be the same as that on Earth. For example, if liquid water is strongly acidic, it will have a lower freezing point, thus staying liquid in a cold climate. But where did the liquid water on Mars come from? Are there any other reasons why stripes can form in Mars gullies? Please turn to the next page.

When the sudden appearance of deep stripes excited many scientists, some people began to question the theory of mountain torrents. Further analysis of gully shows that its shape does not match the shape formed by high-speed water flow. The formation of finger-like deposits shows that particles like fine sand and dry things have impacted the valley. However, the shape of the gully does not completely overturn the possibility of liquid water. Even if gullies are eroded by fine sand, wet conditions may lead to landslides, or a small amount of water may be mixed with sand to form mud.

The first image that caused scientists to guess came from the High Resolution Imaging Science Experiment (HiRISE), which is a camera that can capture tiny terrain details and geological structures. It is one of the six devices that make up the Mars reconnaissance orbiter, and its task is to find evidence of the existence of water. Scientists hope that the mission can also find out the climate and geological characteristics of Mars. However, the scientific load of orbiter mainly focuses on finding H2O.

By now, readers may have realized that the orbiter is not looking for scattered puddles or water bodies that scientists missed in previous Mars surveys. Instead, the orbiter's camera and spectrometer are looking for mineral deposits left by liquid water. Soundsounder uses radar to find underground liquid accumulation. Other cameras monitor clouds and sandstorms. All the information of Mars reconnaissance orbiter is transmitted to Earth by X-band and Ka-band radio waves, and received by the space network antenna in Canberra, Australia.

In the past, orbiting spacecraft have observed two kinds of hydrated minerals on Mars: layered silicate formed by the combination of water and rocks on Mars 3.5 billion years ago, and hydrated sulfate formed by evaporation 3 billion years ago. However, in 2008, the Mars Reconnaissance Orbiter discovered a new hydrated mineral in the form of hydrated silica (also known as opal). These newly discovered minerals were formed when water was exposed to areas affected by meteorites and volcanic activities. These discoveries have been reduced by one billion years on the basis of previous estimates, indicating that Mars may have liquid water at least two billion years ago.

The orbiter also sent back evidence of clay mineral deposition, which can only be formed by rock fracture and liquid water changing landforms in the early history of Mars. Scientists believe that in the distant past of this planet, the flowing groundwater of Mars formed these cracks.

In the past few years, the Mars reconnaissance orbiter was not the only "spy" on the red planet. When the orbiter observed Mars from space, the Phoenix Mars lander entered the Martian atmosphere to explore the surface condition of Mars.

Why water?

We often tend to take water and its properties for granted, but water is actually an unusual compound. Most planetary scientists believe that liquid water is necessary for life. But why? This powerful solvent can easily dissolve various molecules, so that nutrients and metabolism can be recycled.

In May 2008, Mars received a rare visit from the Earth. The Phoenix Mars lander landed in the far north, which has never been developed before to study Martian water. This information can help scientists better judge whether Mars can support the reproduction of life as we know it. After all, if there is a human mission on Mars, the existence of available water may mean that astronauts are missing one piece of equipment during interstellar travel.

The landing site is the main detection area, because there is a lot of solid water under the arid soil layer in the Arctic. Phoenix excavates the surface through its robotic arm, collects samples of soil and solid water, and then analyzes their contents. It sounds like a piece of cake, but it will take earth scientists two days to successfully deploy the robotic arm and prepare for the excavation task.

Although every movement of the lander's limbs took a lot of time and energy, Phoenix succeeded. It confirmed the existence of solid water in the soil, captured the snowfall in the Martian sky, and found evidence of clay and carbonate. The last discovery is particularly noteworthy, because most clay and carbonate on the earth can only be formed in the presence of liquid water.

The lander also found evidence of organic salts, a substance called perchlorate. Some experts believe that this discovery stifles the idea that there is life on Mars, because this salt can quickly decompose organic compounds. But others still have hope, pointing out that some bacterial species on earth can decompose perchlorate. Will life on Mars be similar to these bacteria?

This is not the only new problem for scientists to look forward to the future of mission to mars. Phoenix also uses a sharp temperature conductance probe to detect the fluctuation of water vapor content in the air. Confusingly, this water is not combined in extremely dry soil.

Originally planned to carry out a three-month mission on the surface of Mars, NASA updated the mission twice. Although the cold weather in 10 forced scientists to start shutting down the lander system, it continued to send data to the earth. Spending a cold winter on Mars mainly means that the lander will be frozen and buried in solid carbon dioxide, but NASA hopes to restart the lander when the temperature is warm enough to run the system and the solar panels can collect energy again.

If Phoenix can't wake up from the ashes of Mars in spring, NASA will have to wait several years to install new electronic eyes on the surface of Mars. The next launch of mission to mars will take place in 20 13. At that time, MAVEN, a spacecraft with the evolution and fluctuation of the Martian atmosphere, will travel to this red planet to study the Martian atmosphere through its means. The atmosphere of Mars is very thin, and bare water can only exist stably in the form of solid or liquid. Scientists hope that MAVEN can better reveal the past of water on Mars and whether there is any form of life on Mars, but for now, what we know is that there is water on Mars, but it does not exist in liquid form.

1.WJ encyclopedia

2. Astronomical terminology

3. Science-Xu Qi Ghost-Sarah Dodi &; Robert lamb

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