15-year radar measurements provide new data on the rotation of the planets, their internal structures.
Venus It is a puzzle of adjacent planets and also reveals little about itself. The milky white clouds obscured the cruel scenery that was shrouded in acid Rain and bake at temperatures that can liquefy lead.
Now, new observations from Earth safety are raising the veil on Venus’ most basic properties. By bouncing the radar off the planet’s surface repeatedly over the past 15 years, the UCLA-led team has determined the precise length of Venus days, axis tilt and core size. The findings are published in the journal. Natural astronomy.
“Venus is our sister planet and these fundamental properties are not yet known,” said Jean-Luc Margot, UCLA professor of Earth Sciences, Planetary and Space who led the research.
Earth and Venus have a lot in common: The two rocky planets have similar sizes, masses, and densities. And yet, they evolve along completely different paths. Fundamental factors such as the number of hours in Venus day provide important information for understanding the different histories of these neighboring worlds.
Changes in Venus’ rotation and orientation reveal how the mass spreads internally. On the other hand, knowledge of its internal structure provides an in-depth understanding of planetary formation, volcanic history, and when its surface changes. Additionally, without precise data on planetary motion, future landings can be reduced by as much as 30 kilometers.
“Without these measurements,” Margot said, “we were basically blind.”
New radar measurements show that the average days on Venus lasted 243.0226 Earth days, or about two thirds of the Earth year. Moreover, Venus’ rotation rate is always changing: the one measured value is slightly larger or less than the previous one. The team estimated the length of the day from each measurement and noticed the difference for at least 20 minutes.
“That might explain why previous estimates were disagreed,” Margot said.
Venus’ heavy atmosphere is likely to cause a change. As it moves around the planet, it exchanges large amounts of momentum with hard ground, which accelerates and slows its rotation. This happened on earth as well. But the exchange only adds or subtracts one millisecond from each day. The impact on Venus is much more dramatic, as the atmosphere is approximately 93 times the mass of the Earth and therefore has greater exchange momentum.
The UCLA-led team also reported that Venus was tilted to one side with an accuracy of 2.6392 degrees (Earth was tilted about 23 degrees), improving the accuracy of previous estimates by a factor of 10, repeated radar measurements were also revealed. To see the ice rate The orientation of Venus’ spindle shifted like the tops of children spinning on Earth. This “economic downturn” took about 26,000 years in one rotation. Venus needs a bit more time: about 29,000 years.
With these precise measurements of how Venus rotates, the team calculated that the planet’s axis is approximately 3,500 kilometers away, somewhat similar to that of Earth, although it was not yet possible to conclude whether it was a liquid or a solid.
Venus is a giant disco ball.
On 21 different occasions between 2006 and 2020, Margot and his colleagues aimed radio waves at Venus from a 70-meter-wide Goldstone antenna in California’s Mojave Desert. Minutes later, the radio waves bounced off Venus and returned to Earth. Radio echoes were picked up at Goldstone and at the Green Bank Observatory in West Virginia.
“We used Venus as a giant disco ball,” said Margot, with radio discs acting like a flashlight and planetary landscapes like millions of tiny reflectors. It’s about 100,000 times brighter than a conventional flashlight, and if we follow the reflections from the disco ball, we can summarize its spinning properties. [state]. ”
The complex reflections light up abnormally and soften the reverse signal that sweeps across the globe.The Goldstone antenna sees the echo first and then the Green Bank sees it about 20 seconds later, a definite delay between reception. At both locations, it provides an overview of how fast Venus is spinning, while the moments when its echoes are closest to each other reveal the planet’s tilt.
Observation takes a great deal of time to ensure Venus and Earth are in the right position. And both observatories must be fully functional, which is not always the case. “We find it difficult to get everything to work properly in 30-second intervals,” Margot said. Well then we got some information. But it’s unusual for us to get all the information we were hoping to get. ”
Despite the challenges But the team is moving forward and looking. JupiterEuropa and Ganymede moons Many researchers have strongly suspected that Europa, in particular, hides the oceans of liquid water under thick ice crusts.Radar measurements on the ground could strengthen the oceans and reveal the thickness of the ice crust.
And the team will still bounce off Venus radar. With each radio echo, the curtain over Venus is raised slightly, giving our affiliated planet a sharper view.
Reference: “Venus’s Rotational Status and Moment of Inertia” by Jean-Luc Margot, Donald B. Campbell, Jon D. Giorgini, Joseph S. Jao, Lawrence G. Snedeker, Frank D.Ghigo and Amber Bonsall, April 29, 2021 Natural astronomy.
DOI: 10.1038 / s41550-021-01339-7
This research was supported by NASAJet Propulsion Laboratory and the National Science Foundation
Other researchers involved in the study were Donald Campbell of Cornell University; Jon Giorgini, Joseph Jao and Lawrence Snedeker of the Jet Propulsion Laboratory; And Frank Ghigo and Amber Bonsall of the National Radio Astronomy Observatory in West Virginia.