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This article comes from the official Wechat account: Earth knowledge Bureau (ID:diqiuzhishiju), text: planets do not shine, revised manuscript: Chaoqian

The title of the original text: "well, there is less and less water!" "

On April 28, 2023, Qin Xiaoguang's team from the Institute of Geology and Geophysics of the Chinese Academy of Sciences published an important research result in Scientific Progress, indicating that liquid water once existed on modern Mars. Modern Mars is not the present Mars, but refers to the period between 1.4 million and 400,000 years ago, that is, the late Amazon period of Mars.

Based on the data collected by the navigational terrain camera, multispectral camera and Mars surface composition detector of the Zurong rover in China, this study adds ground observation evidence of liquid water at the low latitudes of Martian. A Martian water cycle model is proposed. This is of great significance for exploring the history of Martian climate evolution.

Above: Zhu Rong photographed traces of water on the surface of Martian dunes

Bottom: the location of water marks in the dunes

(photo: Institute of Geology and Geophysics, Chinese Academy of Sciences / Qin Xiaoguang team) ▼

On May 11, Liu Yang's team from the National Space Science Center of the Chinese Academy of Sciences published another important research on Martian water activities in Science Progress.

The study, based on data from the Zhu Rong rover's navigational terrain camera and short-wave infrared spectroscopy camera, shows that a plate-shaped bright rock on the Martian surface that resembles sedimentary rock is rich in minerals such as water sulfate. This marks the first time that China has detected water-bearing minerals on Mars.

Above: spectral comparison of rocks and rocks observed by Zhu Rong

Below: the schematic model of rock formation process inferred by analysis.

(photo: national Space Science Center of the Chinese Academy of Sciences / Liu Yang team) ▼

After the publication of the above research, the related topics have been widely discussed by the public.

At present, what other Mars exploration missions are related to the exploration of life on Mars? What does it mean for Zhu Rong to discover the existence of liquid water on modern Mars? Could there be life on Mars? Is it possible for humans to move to Mars in the future? Can you grow vegetables on Mars?

Wall-E and Eva on Mars among the eight planets in the solar system, apart from Earth, scientists know the most about Mars and are most interested in it.

Since 1964, a total of 47 Mars exploration missions have been carried out in various countries, of which 25 were successful or partially successful, bringing back a large amount of Martian data for mankind.

Summary of 47 Mars missions

(figure: The planetary society) ▼

These materials continue to refresh people's understanding of Mars, and even overturn the old understanding, but there is no doubt that liquid water once existed on Mars. As a result, Mars has become one of the main targets for scientists to search for extraterrestrial life in the solar system.

In search of possible Martian life, humans continue to launch probes that, in a sense, "follow the current". One of the important motivations is to explore clues of life on Mars.

After all, water is the source of life.

Maybe Mars a million years ago was also a blue planet.

(figure: wiki) ▼

Let's take a look at which probes have so far returned scientific evidence related to liquid water and life on Mars:

In 1996, the Mars Global Surveyor discovered new alluvial deposits formed by water erosion after taking high-resolution photographs of a suspected scouring gully in the Martian Centauri area.

Interestingly, the 2005 Mars Global Surveyor probe

New shock deposits have been found in the same area.

(figure: NASA) ▼

In 2001, the Odyssey Mars probe explored the North Pole of Mars and found traces of water vapor in the Martian atmosphere.

Gamma Ray Spectrometer (GRS) on the Odyssey Mars probe

Large amounts of water have been found in many parts of Mars.

Researchers believe there is enough ice under the Martian surface to fill two Michigan lakes.

(figure: themis.mars.asu.edu) ▼

In 2003, Mars Express detected weathered salt minerals on Mars and discovered a dry salt lake similar to Lop Nur. Salt minerals are residues from the volatilization of water, which provides evidence for the existence of water on the surface of Mars.

In 2004, opportunity confirmed the existence of liquid water on Mars and found chemical evidence such as peridotite, indicating that Mars had an environment suitable for life.

"Robert E" target rock captured by opportunity

(figure: NASA) ▼

In 2011, the Mars Reconnaissance Orbiter photographed seasonal slope lines on the Martian surface or subsurface. Through the study, it is found that the minerals in this seasonal slope pattern region are dissolved in water and then precipitated and enriched, proving that liquid water once existed on Mars.

Slender dark spots on the slope, presumably caused by salt water

These spots move seasonally along the slope near the Martian equator.

(figure: NSAS) ▼

In 2012, Curiosity confirmed the existence of water and a living environment on Mars through an analysis of rock samples.

Curiosity found conglomerate consisting of sand and gravel.

Scientists believe that the shape and size of the pebbles that make up the conglomerate

Suggests that they may have been eroded by water billions of years ago.

(figure: NASA) ▼

In 2014, the Mars atmosphere and volatile Evolution Orbiter captured water molecules at an altitude of about 150km in the Martian ionosphere.

In 2018, Martian Express radar data showed the presence of liquid water under the Martian Antarctic ice sheet.

The top, smooth, bright line is the surface.

Below is the ice and dust.

The blurry bright line below is interpreted as liquid water.

(figure: ESA) ▼

In 2020, Curiosity discovered an organic compound called thiophene on Mars. However, the organic compound can be produced in both biological and abiotic ways.

In 2020, Mars Express radar data showed that the "ancient lake" at Mars' South Pole was surrounded by a "pool" at the 1.5km under the ice.

Analysis diagram obtained from radar data

A value greater than 15 indicates the presence of liquid water ▼

In 2021, images of perseverance suggest that alluvial plains may have been washed away by rivers, and Rochette rocks may have been carried by water from upstream. Olivine, pyroxene, sulfate and carbonate are found in Rochette rocks. This indicates that water once existed on Mars, and the mission took samples of Martian soil and rocks to return to Earth.

After the perseverance sampled the rock,

Don't forget to stay and sign in for selfies.

(figure: NASA) ▼

In 2022, radar data from the Mars Global Surveyor showed that liquid water accumulated under the Martian Antarctic ice sheet.

The Martian Antarctic ice sheet looks like a soft milk cap.

It's actually made of frozen water and frozen carbon dioxide.

(figure: ESA) ▼

In 2023, images from Zhurong show that liquid water exists on modern Mars and is rich in minerals such as hydrous sulfates.

Future missions, such as the ExoMars mission, are still looking for more evidence of Martian hydrology and life.

So far, the position of all Martian landers on Mars

(figure: NASA,wiki,ESA,YouTube) ▼

What does it mean when Zhu Rong discovers that liquid water exists on modern Mars? To sum up, a large number of independent observations show that liquid water once existed on Mars. Although it is impossible to estimate exactly how long liquid water has existed on Mars, it is estimated from the geomorphological features of ancient lakes, alluvial fans and deltas on the Martian surface that liquid water has existed on Mars for at least thousands of years.

Distribution map of ancient Martian lakes, alluvial fans and deltas

Among them, red represents a higher elevation (elevation)

Blue represents a lower elevation (elevation)

(photo: China University of Geosciences / Zhao Jiannan team) ▼

This may mean that Mars had a warm and humid period, when the Martian atmosphere was much thicker than it is now, and there was probably life.

However, scientists have so far found no independent evidence that Mars did have a warm and humid period, and there is no appropriate climate model to explain the problem. Or maybe there was no such warm and humid period on Mars, and there may be another explanation for the existence of liquid water on Mars.

There was also an imagination of a warm and humid period on Mars.

To some extent, it is also the desire of human beings to prove that they are not alone.

Using Zhu Rong's data, Qin Xiaoguang's team offers another possible explanation, that is, the existence of liquid water on modern Mars may be related to the high-angle activity of Mars.

As we all know, many planets in the solar system, including Earth and Mars, are "side-by-side". The rotation axis of the planet is at a certain angle with the axis of rotation, that is, the "yellow-red angle". At present, the inclination of the earth is about 23.44 °. The earth is perturbed by the gravity of satellites, massive planets and the sun, which will lead to periodic changes in the inclination of the earth's axis. The inclination of the earth's axis varies slowly between 21.5 and 24.5 °, with a period of about 40,000 years. This phenomenon will also occur on Mars.

The existence of "Yellow Chijiao Angle"

It is the root cause of the changes of the four seasons and the distinction between the five belts on the earth.

As early as the modern Mars period, Mars may have experienced many periods of large inclination on the Martian axis, and the orbital inclination of ancient Mars was larger than it is now, causing the Martian polar ice sheet to spread to low latitudes, which allowed Mars to produce large amounts of saline liquid water, or liquid lakes, at low latitudes, while in small inclination periods, such as today's Mars, water vapor returned to the polar ice caps from low latitudes. This assumption can well explain the image sent back by the Zhu Rong.

For most of the history of the solar system,

The inclination of Mars is greater than 25 degrees.

Compared to Mars today

This will result in warmer summers and colder winters ▼

A higher inclination may cause a partial melting of Martian water ice.

In the image below, subtle east-west ridges are picked out on the east-facing slope.

Dark and light stripes seem to deflect eastward (downhill) on the ridge

This may be the proof of climate change driven by ancient tilts on Mars.

(figure: NASA) ▼

If so, Mars may have never experienced a warm and humid period, has been in a state of silence, and may not even have the conditions and time to give birth to life.

In fact, so far, not even bacteria have been found on Mars. Scientists no longer expect to find life on Mars today. Almost all the relevant scientific research results are only certain possibilities, and even if the validity of the scientific research results is determined, it is not the same thing as discovering life on Mars.

The fantasy of having a barbecue on Mars with Martians

You can put it aside for a while.

In either case, the existence of life on Mars still needs to be further verified, and the most effective and direct way is to directly detect and sample return, which is also the main mission of perseverance and the future probe. At present, it can only be hoped that perseverance will collect returned Martian rock samples around 2030 (there may be microbes in the crystals of Martian rocks).

Above: Rochette rocks sampled by perseverance

A rotating hole left by a sampler.

Lower: sealed sample tube containing rock samples

(figure: NASA / JPL-Caltech / ASU) ▼

Livable? Emigrate! Mars is the farthest Earth-like planet from the sun, with a reddish-brown surface. The average surface temperature of Mars is lower than that of Earth, and the average atmospheric density of Mars is only about 1% of that of Earth, which is very thin.

The main reasons for the thinning of the Martian atmosphere are the weak magnetic field (only about 0.1% of the earth's magnetic field) and the small mass (about 10% of the earth's mass), which makes it unable to maintain enough atmospheric pressure to prevent the solar wind from blowing it into space.

Escaped Martian atmosphere captured by ultraviolet spectrometer

(figure: NASA) ▼

As a result, the diurnal and seasonal temperature difference is much larger than that of the earth. Martian temperatures can drop to-140 degrees Celsius at night in winter and as high as 35 degrees Celsius during summer days. Even in the same season, the temperature difference between day and night on Mars can exceed 100 degrees Celsius.

There is no doubt that this temperature environment is still very bad, but it is much better than other celestial bodies such as Venus, Europa and Ganymede. They are thought to be celestial bodies that may have signs of life in the solar system. In 2020, scientists detected phosphine molecules in the high clouds of Venus, which may be the result of anaerobic metabolism. Europa and Ganymede are thought to have subglacial oceans and may have life at suitable temperatures.

Europa and Ganymede often become human "space colonies" in science fiction.

However, if you want to emigrate here, you have to face many problems, such as low temperature, high radiation and so on.

From this point of view, Mars is indeed more "fragrant".

(figure: NASA) ▼

In addition, the rotation period of Mars is about 24 hours and 37 minutes, which is close to that of a day on Earth, unlike "living like a year" on Venus (the rotation period of Venus is greater than the rotation period, that is, "one day" is greater than "one year"). The angle between the rotation plane of Mars and the rotation plane is about 25.19 °, which is close to the 23.44 °of Earth, which means that there is also spring, summer, autumn and winter on Mars.

Mars is located on the periphery of the habitable zone of the solar system (the habitable zone refers to the specific zone around the star, in which the surface temperature of the planet orbiting the star is moderate, allowing water to exist as liquid on the surface). Although the surface temperature of Mars may reach the temperature of liquid water in some places, because its atmosphere is extremely thin and lacks strong magnetic field protection, it is difficult for water to exist on the surface of Mars for a long time. And it can't adjust the temperature like the earth.

As a result, Mars is not currently considered a habitable planet.

The livable zone of the solar system

According to the out-of-control algorithm of Greenhouse Effect and Water loss

It is concluded that the livable zone of the solar system is 0.99-1.688au.

(figure: Cornell University) ▼

But Mars is also the only planet in the entire solar system that may have been modified for large-scale migration. One of the advantages of moving to Mars is that it is rich in water resources. At present, it has been proved that the reserves of water resources on Mars are huge. If all of them are thawed and thawed, they can cover the entire Mars for more than ten meters.

If the aforementioned Antarctic ice sheet melts

Will be enough to cover the entire surface of the earth at a depth of 11 meters

(ice-filled Koroliov crater near the North Pole)

(figure: ESA / DLR / FU Berlin) ▼

In addition, Mars has an atmosphere that can block some of the radiation. With the relocation of the habitable zone of the solar system in the future, Mars will become warmer.

The main disadvantage of migrating to Mars compared to moving to the moon is the high cost of transporting materials, but this is also predictable.

In the future, if we can make full use of the in-situ resources on Mars, through 3D printing building materials, water recycling and biological and artificial oxygen production technology, we can greatly reduce the transport volume and reduce the construction risk and cost of Mars. Opening up wasteland on Mars like in the movie "Martian" will no longer be science fiction, but will become a reality.

As long as the technology exists, we are not afraid of the difficulty of opening up wasteland.

(photo: Martian) ▼

The Martian has a line: "once you plant crops somewhere, that place is your colony." So, can you grow vegetables on Mars? The attitude of scientists is optimistic. Although the Biosphere 2 project failed, it is reliable and feasible to maintain the growth of crops through man-made physical and chemical regulation.

Solved the food problem.

It's equivalent to solving half of the survival problem.

(photo: Martian) ▼

Because Martian soil also has a lot of minerals needed for crops to grow, and crops require much less air pressure than humans (only 5% of the air pressure on the earth's surface), the requirements for "greenhouse" building materials for farms are greatly reduced.

Once you can successfully grow vegetables on Mars, it means that self-sufficiency on Mars will become possible, and even a certain degree of "geochemical" transformation of Mars can be carried out.

Establish the magnetosphere, establish the atmosphere, and raise the temperature.

Some on Earth can also be found on Mars.

(blueprint of the Mars transformation process: wiki) ▼

There are bound to be technical, financial, political and ethical difficulties, which require the attention of human beings. Currently, NASA is working with SpaceX to plan to send humans to Mars by 2030, which may be the prelude to moving to Mars.

There are still about ten years to go before the planned human landing on Mars

To rally people and overcome the immediate difficulties.

The result will be revealed by time.

(figure: YouTube@spacex) ▼

From searching for life on Mars to moving to Mars, the image data sent back by the Mars probe represented by Zhu Rong lit up the hope in our hearts. This is the first sound of mankind's oath on the road to the universe, and it will also become an important chapter of human hymns.

Reference:

1.Xiaoguang Qin et al., Modern water at low latitudes on Mars: Potential evidence from dune surfaces.Sci.Adv.9,eadd8868 (2023). DOI:10.1126/sciadv.add8868.

2.Yang Liu et al., Zhurong reveals recent aqueous activities in Utopia Planitia, Mars.Sci. Adv.8,eabn8555 (2022). DOI:10.1126/sciadv.abn8555.

3. Zhao Jiannan, Shi Yutong, Zhang Mingjie, etc. Advances in the study of Martian hydrogenic geomorphology [J]. Acta Geologica Sinica, 2021 and 95 (09): 2755-2768.DOI:10.19762 / j.cnki.dizhixuebao.2021267.

4. Lu Changhai. Explore the trace of life-Mars [J]. Knowledge of Modern Physics, 2016. 28 (03): 23-30.DOI:10.13405 / j.cnki.xdwz.2016.03.012.

5. Https://solarsystem.nasa.gov/planets/mars/in-depth/

6. Https://www.planetary.org/space-images

7. Https://www.sciencenews.org/article/mars-perseverance-rover-nasa-water-life

8. Https://www.sciencenews.org/article/mars-lake-south-pole-ice-surrounded-pools-water

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