Scientists have parted the clouds on Venus, our shrouded neighbor, revealing the length of its day, the rough size of its core, and the tilt of its axis. All this took almost 15 years to figure out. Between 2006 and 2020, Jean-Luc Margot and colleagues at the University of California, Los Angeles, bounced radio waves off Venus using the Goldstone Solar System Radar in California's Mojave Desert. Across the country in West Virginia, the Green Bank Telescope tracked the echoes on return. This revealed that an average Venus day lasts 243 Earth days, though one day is not necessarily as long as the next. The length of day fluctuated by up to 21 minutes over the study. Scientists attribute this to Venus' heavy atmosphere pushing and pulling the surface. The same thing happens on Earth, but as our atmosphere is much lighter, "the exchange adds or subtracts just one millisecond from each day," reports Phys.org.
The team, whose findings are published in Nature Astronomy, found Venus' axis tilts at 2.6392 degrees, compared to Earth's 23 degrees, and wobbles in a rotation that would take 29,000 years to complete. That process takes about 26,000 years on Earth. This allowed researchers to estimate that Venus' core has a radius of 2,175 miles, much like Earth's. There are still lots of unanswered questions, including whether "Venus has an inner solid core and an outer liquid core, like Earth, or if it’s all solid or all liquid," Margot tells New Scientist. Still, insight into Venus' interior structure is important as "it's really difficult to understand anything about a planet" without it, Margot notes. It "fuels insight into the planet's formation, its volcanic history and how time has altered the surface," per Phys.org. Margot notes the data will also be crucial in case of future landings. (Venus hosts a chemical known to come from living things.)