Liquid water may have “recently” flowed on Mars revealing the location of the sorae gateway to space

「MarsThere are countless valleys on the surface”, some of which appear to be traces of a fluid that flowed very recently. But today’s cold and dry Mars is unlikely to explain the flow of liquids in volumes large enough to leave marks on the terrain. However, a research team led by JL Dickson of the California Institute of Technology that if the axis of rotation of Mars were tilted more than it is today,Liquid water could exist on Mars persistently enough to form valleysI discovered it. It is believed that such phenomena have occurred many times over the past millions of years.The last one occurred about 630,000 years agoIt is believed that

Various topographic features carved on the surface of Mars tell us that there was a large amount of liquid water in the past. However, Mars is currently extremely dry, and there is not even solid water on its surface, let alone liquid water, except in the polar regions.

Mars is believed to have reached its low temperature and thin atmosphere about 3 billion years ago. In such an environment, water would sublimate directly from the ice to water vapor, so the ice on Mars today is mainly carbon dioxide ice (dry ice).

On the other hand, if you look closely at the surface of Mars, you can find many recently formed valleys on the slopes of craters and plateaus. Due to the large amount of carbon dioxide on Mars, these valleys are thought to have formed through carbon dioxide sublimation.

However, there was a problem that the typical shape of the valleys generated during the phase change of carbon dioxide from a solid to a gaseous state did not match the shape of the actual valleys found on Mars. In order to better explain the shape of the valleys, we have to assume that they are traces of some kind of fluid flow.

Now that we can send a lander to the surface of Mars, it has been found that there is a large amount of solid water, in other words, ice, just below the topsoil. In other words, depending on the conditions, the ice buried beneath the topsoil may melt, creating a flow that carves the valley.

This is a process that can also be seen in Antarctica on Earth. Antarctica appears frozen due to the extremely low temperatures, but during short summers temperatures can get high enough to form currents that flow only during the day. However, it was not known whether such a calm environment actually existed on Mars in recent times.

Dixon’s research team is trying to determine what kind of climate each region of Mars will experience when the tilt of Mars’ axis of rotation is shifted to different values, and whether liquid water can exist under such a climate. Currently, the axis of rotation of Mars is tilted 25 degrees with respect to the orbital plane, and we have investigated how much of this value to create a suitable environment. The “suitable environment” mentioned here is limited to cases where the surface temperature exceeds 0°C and the surface pressure exceeds 612 Pa. (※ 1) 。

*1… This is based on 0.01℃ and 611.657Pa, which is the triple point of water (the point where solids, liquids, and gases reside). Liquid water will only appear if the temperature and pressure exceed this value. On Mars today, this condition is only achieved for a very short period of time near the equator during the summer.

Of particular note is the fact that most of the newly carved valleys are distributed at high latitudes in the southern hemisphere. Since 78.4% of the new valleys are strongly skewed between 25°S and 50°S, our simulations focused primarily on probing the conditions under which high latitudes in the Southern Hemisphere would experience a more temperate, rice paddy environment.

First, if the inclination of the axis of rotation was 25 degrees, as it is today, then the average atmospheric pressure would be 600 Pa, and the altitude at low and middle latitudes would be 2500 meters. (※ 2) It has been found that liquid water can exist for very short periods of time in spring and summer in the lowlands below. However, there are almost no valley lines in such areas. In fact, it is estimated that the equatorial region of Mars is much drier than the higher latitudes, and even if environmental conditions are met, valleys will not form.

*2… The altitude on Mars is determined to be 0 meters when the surface pressure is 610.5Pa, which is about the same as the triple point of water.

On the other hand, different results were obtained when the axis of rotation was tilted more than it is now. When the inclination is 30 degrees, the average atmospheric pressure is 800 Pa. It has been found that the area with the valley line in the northern hemisphere is an environment where liquid water can exist. For example, it is estimated that liquid water can exist at 30°N latitude for about 13% of the year. However, it contradicts the existence of many valleys in the Southern Hemisphere, as the pressure does not exceed 612 Pa in many areas of the Southern Hemisphere, and it is estimated that liquid water cannot exist.

【▲ Figure 2: Simulation results of whether or not liquid water can exist at different angles of the axis of rotation. The more yellow the colored dots are, the more likely it is that the climate is liquid, and the black dots indicate where the valleys are. The best match is the 35° rotation axis (panels E and F). The area of ​​the white square shown in Figure 4 in Figure F corresponds to Figure 1 in this article (Credit: Dickson, et.al.)]

but,The inclination of the axis of rotation is greater than 35 degreesThe average atmospheric pressure is 1200 Pa whenDepending on the season and time of day, it becomes an environment where liquid water can exist.I understand. In particular, it was found that liquid water can only exist at altitudes below 4,500 meters in latitudes higher than mid-latitudes. This is consistent with the presence of valleys at high latitudes in the southern hemisphere and the absence of valleys above 4,500 meters above sea level, which is most consistent with true Mars.

Dixon and his colleagues estimate that the tilt of Mars’ axis has reached 35 degrees several times over the past few million years, and that liquid water that flowed in at that time had carved these valleys. More recently, it has been estimated that such an environment occurred around 630,000 years ago, but that is very recent in the billions of years of Martian history. As mentioned above, the current axis of rotation of Mars is tilted by about 25 degrees, but such changes may occur in the future.

This discovery is further evidence that Mars is not as barren as previously thought. Future Mars exploration missions may be able to detect traces of life by examining these relatively recently formed valleys.

source

• JL Dixon and others. “The grooves on Mars could be the result of melting water ice during periods of high declination.” (Sciences)
• Juan Celizar. The study notes that “grooves on Mars may have been formed by recent periods of liquid meltwater.” (Brown University)
• Samuel C. Shawn, James W. Head, and Caleb I. Fassett. “A Unique Chronostrategeographic Marker in Sedimentary Fan Layers on Mars: Evidence for Ca. 1.25 M Gross Activity and the Origin of Surface Meltwater.” (geology)
• James L Dixon and others. “Recent Climate Cycles on Mars: Stratigraphic Relationships Among Multiple Latitude-dependent Canyon and Mantle Generations”. Follow Favorite

Text: Rare Aya