When the planets revolve around the Sun, separated by a good distance, we think that they do not contact at all and do not exchange material. The solar system can be a violent place in which asteroids fall and comets fly, but the planets themselves seem too large and massive to be involved in any way. When big energy shocks hit your planet, the worst they can do is make a hole, leave a crater, and cover the world with dust and debris.
But sometimes, if the impact is strong enough, it can throw all the debris into space. Many of the satellites in our solar system, including those of Earth, Pluto and Mars, were created from the merger of this debris after a giant impact. Some of the debris fell back onto the planet, while other remaining matter was ejected from the entire planetary system.
Can a stone from one planet fall on another?
In theory, yes, material from one planet can be transferred to another.
In practice, we know that this is the case. Pieces of Mars were found on Earth, and new ones fall on our world every few years.
The science of meteorites is beautiful and interesting. More than 61,000 pieces of extraterrestrial rock have been discovered on Earth. The solar system is a diverse and intricate place, and every body that has ever fallen on it or from which we took samples is different from others. The rocks on the surface of Venus are different from those found on asteroids, comets, Mars and Earth. In fact, they all differ in composition among themselves, like the rocks that we have seen on various satellites that we have visited, such as Titan's satellite Saturn.
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The only rocks that we know have a similar composition are those of the Earth and the Moon. The similarities between terrestrial rocks and lunar samples speak for a giant impact in the early history of the solar system that led to the appearance of the moon.
In the case of any stone on Earth, regardless of its origin, we can analyze what elements of the periodic table it consists of, as well as what are the ratios of the isotopes of these elements.
For example, one notable piece of evidence that the grand extinction event 65 million years ago began after the fall of an asteroid is a layer of ash found all over the world, since the ash of that time contains 10 times more iridium in density than any rock on Earth. … This is quite natural for asteroids, so we consider them the main prerequisite for the extinction of dinosaurs and the flourishing of mammals.
Objects that land on Earth, however, are in a separate category. Instead of wandering in space, they travel through the solar system and collide with our world, with many falling to the surface and leaving footprints. These meteorites come in many different types. They have different densities, different compositions of elements and different geological features inside. Most meteorites are rocky and contain small, rounded particles, mostly silicon inside. These types of meteorites are known as chondrites and account for 86% of all meteorites. Another 8% are also rocky, but without these molten silicon particles inside: achondrites. Another 6% is iron meteorites, a mixture of stone and metal.
And while this includes every meteorite we have ever found, they are not created the same or even typical. Some of them are even strange. Three different types stand out separately:
Shergottites: volcanic rocks rich in both magnesium and iron, with varying crystal sizes and mineral contents within, and appear to have crystallized recently, perhaps as little as 180 million years ago.
Nachlites: These are much older, formed between 1.3 and 1.4 billion years ago, also through volcanic activity. They are rich in the mineral augite and contain evidence that they were flooded with liquid water about 620 million years ago.
Chassinite: These meteorites are almost exclusively made from the mineral olivine with added pyroxene, feldspar and oxides. They contain noble gases that differ in composition from the Martian atmosphere, which indicates their origin in the planet's mantle.
All three of these types differ markedly from other meteorites found on Earth, but have elemental and isotopic commonality. The ratio of oxygen isotopes in them, in particular, differs from the ratio in other meteorites, and they also have an earlier formation time. For a long time, scientists have suspected that they may have a similar origin, which distinguishes them from more typical meteorites.
In 1976, the Viking lander brought us information about the surface of Mars, including information about the Martian atmosphere and rocks found on the surface. The similarities were striking, and many thought that all three types of meteorites were from Mars. But the real evidence came in 1983, when trapped gases were found in the glass formed during the fall of one of these Shergottites, and these gases were consistent with those found by the Viking on Mars.
There were 207 known Martian meteorites in 2018. Based on radiometric dating, we can conclude that the meteorites that hail from Mars are extremely young: only 3 of those hailing from Mars are over 1.4 billion years old; most were formed several hundred million years ago.
In addition, we can tell how long they traveled based on their contact with cosmic rays, which ranged from 730,000 years to 20 million years. In any case, the formation of these meteorites on Mars was relatively recent in terms of geology, and when they hit Earth, mammals were already dominating the planet.
You don't need to be the size of a dinosaur-killing asteroid to eject material from a planet, and these impacts apparently happened often enough to transfer material from one planet to another within the solar system. Approximately 0.3% of all meteorites that fell to Earth are of Martian origin, which gives food for thought about the origin of life - perhaps it came to Earth from Mars or other planets in the solar system. People have not yet been to another planet, but thanks to natural processes, other planets regularly visit us. Pieces of Mars are found all over the planet. If we try, we might find pieces of Earth on other planets that we have yet to visit.
Ilya Khel
