Why did Venus “turn upside down”?  |  Urania

The second planet from the Sun is hot, inhospitable and still full of secrets. The brightest planet in our sky is always surrounded by thick clouds that have thwarted previous attempts to explore it.

Likewise, the first modern efforts to explore Venus in the 1960s and 1970s were only half-successful, marked by numerous setbacks and a short lifetime for landers to successfully reach their destination. It turns out that, contrary to what was previously thought, Venus The conditions are very hostile. Some landers did not have time to send the data recorded there to Earth, because they were destroyed by the enormous pressure and temperature. The first temperature measurement on Venus by the lander showed 430 degrees Celsius, after which this instrument also failed. Subsequent spacecraft sent there by the United States and the Soviet Union later recorded higher temperatures and crushing pressures, making their return data stream short-lived. In the 1970s, Soviet and American missions landed and orbited Venus, giving us a better understanding of the extreme conditions on Earth's closest planet. But the real achievement came only with the American Magellan probe, which carried out a radar mapping mission of Venus in 1990-1994. Hence the famous radar images showing the real Venus.

Magellan revealed many surprises, but the most important of them came when scientists analyzed radar images of the planet's surface. What was most striking when examining the radar images that penetrated the thick cloud layer was that there were very few craters on the surface of Venus. This was surprising for a terrestrial planet in the inner solar system. The potholes must be there! Planetary scientists know that in the early history of our system, its inner region was inundated by a large number of impacts. This happened during what is now known as Late Heavy Bombardment, about 4 billion years ago, when planetesimals and other small celestial bodies moved widely and freely through the system before eventually being removed by numerous collisions.

Well-preserved records of this process can be seen on Mercury and the Moon. The situation on Earth is somewhat different, where – as we know – many surface renewal processes, that is, erosion, occur. These processes destroy the pits over time. Only a few, such as the famous and the great, can survive Crater Baringera In Arizona, it is considered the best preserved crater on Earth. It was likely preserved due to the desert climate at the site of the impact: water erosion destroys it very slowly and the weakness of the surrounding vegetation does not encourage its growth. Wind erosion is almost imperceptible there. But most of Earth's craters have suffered the opposite fate. However, it is still unknown how this happened on Venus, a planet where typical erosion does not occur.

Venus is a strange place in many ways. Devastating temperatures, a carbon dioxide-rich atmosphere, and incredibly high pressure combine to create a terrifying sight. Unlike Earth, Venus also has no tectonic plates to help hide ancient craters. If all the water in Venus's atmosphere were condensed into a layer at the surface, it would be only 10 cm deep. The modern deuterium-to-hydrogen isotope ratio on Venus suggests that much more water than was present early in the planet's history would have escaped into space long ago.

The Magellan probe's astonishing discovery that the surface of Venus is very young is also key to understanding its history. Magellan collected radar images showing about 98 percent of the planet's surface. It also captured data on its gravitational field. This and other information allowed scientists to create a physical model of Venus. They also revealed that the planet is rich in… Shield volcanoes And lava plains. Many of its highlands were formed around areas similar to high volcanic areas on Earth, such as Hawaii and the Canary Islands. There are also 'strange' tectonic features, some of which are unique to Venus, e.g ticketsfrequently cracked areas, or the crowni.e. rounded shapes that may have arisen from streamed columns.

All of this was very shocking to planetary scientists at the time. It has become clear that at some point in the past, massive volcanoes covered the older surface of Venus. But what could be causing this catastrophic global resurfacing? We still don't know that. All we know is that the surface of Venus was theoretically supposed to be 3 or 4 billion years old, but a major event inside it likely turned the planet upside down less than a billion years ago and covered most of it with a new lava-rich layer. Surface.

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Source: astronomy.com/David J. Escher

Prepared by: Elizabieta Kolegoska

In the illustration: Spectroscopy allows us to identify planets that are potentially suitable for life. Although the three planets in our system shown here show very high spectroscopic data for carbon dioxide, only Earth can also identify evidence of water, ozone, and carbon dioxide. (NASA, ESA, CSA, Kristin Klicka (STScI))

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