Revealing the background of the geology that makes Earth a strange star, different from other planets in the solar system.
Geosphere – Different types of rocks that are common in the world. It is considered a rare object found on neighboring planets in the solar system. Why is this so? And what makes rocks on Earth unique?
Not long ago Scientists have made a surprising discovery on the moon’s far side: a hotspot, a volcanic crater that collapsed billions of years ago. The higher temperatures in that area are caused by radioactivity in the granite on the moon’s surface. It is caused by magma that has cooled through cracks on the surface of the star.
The surprise, however, was not the radioactivity in the granite. Because even the granite on Earth that is used to make kitchen countertops contains a small amount of radioactivity. But what was really surprising to scientists was “Finding that there is granite on the moon,” although we can find this type of rock everywhere. Because our tectonic plates are constantly moving and there is water on our planet. But on the moon, neither of these factors would allow granite to form.
When the geological data of rocks on Earth and other planets in our solar system are compared, it will be found that In addition to granite There are also some types of igneous, sedimentary, and metamorphic rocks that are common on Earth. But it is difficult to find on other planets. Because of this, the landscape on Earth, such as the large and small limestone islands that line Halong Bay, Lava rock and volcanic sedimentary rock interlayer to form Mount Fuji. or even quartz sediments that accumulate to form sand dunes It does not appear on any other planets.
That is, the geology of rocks on Earth is very unique. Therefore, the type of rocks is completely different from other planets.
at present Scientists study and discuss information about rocks on Earth that are special, rare, or rocks that cannot be found on other planets based only on current knowledge. If lunar exploration continues to surprise geological scientists, The geology of other planets that humans have previously explored using robots and unmanned spacecraft. Or exploring it through observing orbits and space telescopes would have surprises just like exploring the moon.
Lithosphere Granite and other rocks formed from recycled magma.
Igneous rock that is formed from lava (or magma that erupts from cracks in the planet’s crust) is just a normal, unremarkable rock in our solar system. There are many volcanoes on the surface of the moon, Mars, Mercury, Venus, and even Jupiter’s moon Io. However, magma beneath the planet’s surface is not the origin of granite. Because before this type of stone could be formed The magma must first go through a recycling process.
Harry McSween, a planetary geology scientist at the University of Tennessee, said: “Normally, newly erupted magma that cools in a planet’s crust forms the black rock we call basalt, not granite.” Typically, granite is formed from repeated molten magma. It came with some of the planet’s crust melting into the mix. As the magma melts, minerals that make up the magma and the planet’s crust, such as quartz, melt easily. It transforms into a liquid and separates from the magma layer. Those liquid minerals are the product of magma recycling. When it cools, it hardens into various types of granite, which is the most common type of rock in the earth’s crust.4
The recycling process of magma usually occurs in subduction zones, or areas where oceanic crust sinks beneath continental plates. The reason is because when the two types of tectonic plates move in opposition to each other, there is friction causing the temperature in that area to rise. In addition, rocks that contain water are also easily melted. When the oceanic crust moves down The water that makes up the Earth’s crust becomes what makes it easier for the plates to melt and turn into magma.
Matthew Siegler, a planetary scientist at the Planetary Science Institute in Tucson, Arizona, who helped locate granite on the moon, said: “A world with both continental and oceanic plates has the potential to easily form granite at any time. But other planets don’t have these things.”
All of this is why Mercury, Venus, Mars, or the volcanic moons of Jupiter have large amounts of basalt. But there was only a small amount of granite. And the reason why granite is so rare on neighboring planets is also why volcanoes on other planets resemble flat pancakes more than Mount Fuji. The answer is because molten basalt is liquid. As the recycled magma spreads out, it becomes shaped like a giant shield. Like Olympus Mons on Mars.
Sandstone and other rocks that were deposited underwater
The abundance of water resources is what gives Earth its unique characteristics from other planets in the solar system. Earth’s water isn’t the only one responsible for helping to melt tectonic plates and rocks. But it also helps various sediments come together and harden until they become a new type of rock.
Various types of sedimentary rock, such as sandstone, are formed when the sediment of weathered rocks accumulates and accumulates until it hardens into new rock. Pressure is what allows this process to continue. But it is not enough to cause the sediment to coagulate. “You need water to bind the particles together,” said Kirsten Siebach, a Mars geologist at Rice University.
What Seabak explains points out that Water is the reason why sedimentary rocks are so difficult to find on other planets, says Bethany Ehlmann, a planetary scientist at the California Institute of Technology. “Although it’s hard to find. But scientists have found that sedimentary rocks are hidden in some asteroids. For example, Asteroids Ryugu (Ryugu) and Asteroid Bennu (Bennu), which were formed when various rock fragments in space, including sedimentary rock, were compressed by the gravity of the two asteroids. turned into lumps”
In addition to the planet Earth Mars is also a planet that has various types of sedimentary rocks on its surface. This is because millions of years ago this planet used to have a lot of water. And there used to be warmer temperatures than today. Most of the rocks found on Mars were formed from sediments deposited in rivers, lakes, and sand dunes billions of years ago. Sibaek added: “Like granite, most of the sedimentary rocks we are familiar with are actually unique types of sedimentary rock that can only be found on Earth.”
Take, for example, sandstone. Sand on Earth is usually white and contains quartz as the main component. Because it is a mineral that is commonly found in granite. With granite it is difficult to decompose. When it decays, it becomes sandy sediment that is deposited until a new type of rock is formed. Sandstone on Mars is made from material that is completely different from Earth. McSween said. “If you don’t count fossils Quartz-based sandstone is probably one of the most unique rocks on Earth that I can imagine. Because in order for a piece of sandstone to form, it requires both tectonics, erosion, and water.”
Limestone and other rocks formed by living things
Tectonics and water are not the only two factors that differentiate Earth from other planets. Because our world is the only planet in which life exists, it is one of the factors that make the rocks found have unique characteristics that are not similar to rocks on other planets.
Limestone is a fine-grained rock that is formed from carbonate sediments in the sea. Limestone is a type of rock that can be found everywhere on Earth because many living things can create this type of rock. For example, Shellfish and various marine animals, especially coral reefs When these animals die, they sink to the bottom of the sea. Limestone will begin to form on remains, whether shells, skeletons, or coral remains. If these limestone remains stuck together They will turn into gigantic limestone blocks.
Sibaek said. “Living things accelerate the formation of limestone much faster. Sometimes even geologists think that Limestone can only be formed by living things.” But processes that do not involve living things can also create carbonate-rich rocks like limestone. It can be created from two elements: Shallow, warm temperature water that is not too acidic. and carbon dioxide In the past, both of these things were things that existed on Mars.
The warm, wet climate of the past has made Mars the best planet after Earth to find carbonate minerals. But Ellmann said: “But if there were no living things that could produce a large amount of this mineral, We don’t think there will be as much carbonate on Mars as there is in Earth’s oceans.”
Scientists have also found trace amounts of carbonate minerals on asteroids, including Bennu. and the dwarf planet Ceres (Ceres), which is close to Earth.
Marble and other stones are transformed by heat and pressure.
Finding marbles in space is very unusual. Not only because it originates from limestone. But marble is a stone that is formed by changing with heat and high pressure without going through the melting process until it becomes a new type of stone.
The transformation of rocks on Earth usually occurs slowly deep underground. Heat and pressure deep beneath the Earth’s crust transform rocks and minerals, turning granite into diamond. and the limestone became marble. But on other planets The transformation of rocks takes place within a fraction of a second from the impact of a meteorite hitting the planet at high speed.
McSween said. “The rocks on those planets are exposed to extremely high pressures and temperatures. But it will only happen in the blink of an eye.”
Shock metamorphism is common on Mars. However, scientists have also found evidence that rock metamorphism is less severe than shock metamorphism on Mars. And the transformation of rocks in the aforementioned ways is similar to the processes that occur on Earth. Instead, change will occur more slowly and gradually. Ellmann and her team have previously identified metamorphic rocks from Mars that she considers They may have formed from high-temperature groundwater circulating through rocks buried beneath the surface of the planet, causing the rocks to metamorphose from the heat and low pressure.
Meanwhile, the surface temperature of Venus is hot enough to melt lead. The planet’s temperature was so high that Max Sween thought the rocks on its surface should have metamorphosed. However, scientists found that Venus’s atmospheric pressure is very low compared to the pressure beneath it. The surface of the Earth is only a few kilometers deep. In other words, although the air pressure on Venus is much higher than on Earth, it is nowhere near the enormous pressure that exists only a few kilometers below the Earth’s surface. Therefore, the force Acted by the weight of the rock layers deep beneath the surface, the Earth is much higher than Venus.
McSween said. “Ultimately, if we can drill deep enough into the surface of the planets, we may be able to find metamorphic rocks on every planet in the solar system.” However, what makes Earth unique is that Earth’s tectonic plates are constantly moving. and various types of rocks that are formed from magma These two factors are the main factors that make our world more geologically diverse than other planets.
McSween also said. “In addition, Our planet also has an efficient process of changing the characteristics of terrestrial rocks. Change occurs in cycles. When rocks from below the surface move up into the earth’s crust. Earth sends rocks on the surface back down into the crust to transform them into new rocks. This is a process that certainly does not happen on any other planet.”
About Elise Cutts
Translation Panthipa Phromket