Science. The days are especially long on Venus

Madrid, 30 (Europe Press)

Outstanding questions such as the exact length of a day on Venus, the tilt of its axis, and the size of its core have been resolved by radar signals repeatedly sent from Earth to its steamy, cloudy surface.

“Venus is our sister planet, yet these basic properties remain unknown,” said Jean-Luc Margot, a professor of Earth, Planetary and Space Sciences at the University of California, who led the research published in Nature Astronomy.

Earth and Venus have a lot in common: both rocky planets have the same size, mass, and density. However it has evolved in completely different ways. Fundamentals such as the number of hours in Venus’ day provide important data for understanding the varying dates of these neighboring worlds.

Changes in the rotation and direction of Venus reveal how the mass is distributed inside. Knowledge of its internal structure, in turn, fuels an understanding of the planet’s composition, its volcanic history, and how time has changed the surface. Moreover, without accurate data on how the planet moved, the distance between any future landing attempts could be up to 30 kilometers. “Without these measures, we would basically be flying blind,” said Margot.

New radar measurements show that the average day on Venus lasts 243,0226 Earth days, about two-thirds of Earth’s year. Moreover, the rotation speed of Venus is always changing: the value simultaneously measured will be slightly higher or lower than the previous value. The team estimated the length of the day from each of the individual measurements and observed differences of at least 20 minutes.

“This may explain why previous estimates do not match each other,” Margot said in a statement.

It’s possible that the dense atmosphere of Venus is responsible for the difference. As it scatters around the planet, it exchanges a lot of momentum with the solid Earth, causing it to speed up and slow its rotation. This also happens on Earth, but the exchange only adds or subtracts one millisecond out of each day. The effect is even more dramatic on Venus because the atmosphere is about 93 times larger than the mass of Earth, so you have a greater incentive to trade.

The UCLA team also reported that Venus is tilted to one side with an accuracy of 2.6392 degrees (the Earth is tilted around 23 degrees), an improvement in accuracy over previous estimates by a factor of 10. Repeated radar measurements revealed more ice-rate. As Venus’s axis of rotation changes, just like a baby’s spinning top. On Earth, this “initiative” would take about 26,000 years to produce a single revolution. Venus needs more time: about 29,000 years.

Using these precise measurements of how Venus is rotating, the team calculated that the planet’s core has a diameter of about 3,500 kilometers, which is very similar to Earth, although they cannot yet infer whether it is a liquid or a solid.

On 21 separate occasions between 2006 and 2020, Margot and her colleagues directed radio waves to Venus from the 70-meter-wide Goldstone antenna in the Mojave Desert, California. A few minutes later, those radio waves bounced off Venus and returned to Earth. Radio echo is captured at Goldstone and the Green Bank Observatory in West Virginia.

“We are using Venus as a giant disco ball,” Margot said, the satellite dish acts as a flashlight, and the planet’s landscapes are millions of tiny reflectors. “We illuminate it with a very powerful flashlight, about 100,000 times brighter than a typical flashlight. And if we follow the reflections of the disco ball, we can deduce its characteristics. [estado] Transformation “.

Complex reflections illuminate irregularly and attenuate the return signal transmitted through the ground. The Goldstone antenna sees the echo first, then Green Bank after about 20 seconds. The subtle delay between reception at the elbows provides a quick glimpse into the rotation speed of Venus, while the specific time window in which the echoes of the echoes are largely similar reveals the tilt of the planet.

The observations required superb timing to ensure that Venus and Earth were placed correctly. And both observatories had to function perfectly, which was not always the case. “We found it really hard to get everything working properly in 30 seconds,” said Margot. “We get some data most of the time. But it is very unusual for us to have all the data we hope to have.”

Despite the challenges, the team forges ahead and sets their sights on the dps of the moons of Jupiter, Europa and Ganymede.