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Japan's Akatsuki spacecraft, also known as the Venus Climate Orbiter, has officially been declared dead by the Japan Aerospace Exploration Agency (JAXA) as of October 28, 2024. This marks the end of humanity's last active mission orbiting Venus. Despite initial setbacks, including a failure of its main engine that prevented it from entering Venus orbit on its first attempt, Akatsuki managed to survive and eventually succeeded in orbit insertion using only its smaller thrusters in 2015. This was a pioneering feat since such an orbital insertion method had never been done before. The spacecraft outlived its planned 4.5-year lifespan by nearly a decade, contributing significantly to our understanding of Venus despite numerous challenges.
Launched in 2010 with a $300 million budget, Akatsuki faced a major engine failure shortly after launch, missing its original chance to orbit Venus. However, the team’s ingenuity allowed the probe to make a second attempt five years later, when it approached Venus after orbiting the sun. The mission’s primary research focus was the study of the thick cloud layers of Venus located 50 to 70 kilometers above the planet’s surface. These clouds exhibit extreme wind speeds, reaching velocities comparable to Japan’s Shinkansen bullet trains, a phenomenon known as “super rotation.” This rapid atmospheric movement is particularly intriguing given Venus’ incredibly slow rotation, with one day lasting about 243 Earth days.
Akatsuki’s observations helped scientists understand that the planet’s clouds accelerate depending on local solar time, indicating that solar heating plays a key role in driving these high-speed winds. This discovery has wider implications for the study of tidally locked exoplanets, where one side of the planet always faces its star. Without mechanisms to redistribute heat, atmospheres on such planets could collapse on their night side. Akatsuki’s findings suggest that thermal energy input from a star might help maintain atmospheric circulation even on tidally locked worlds, potentially impacting their habitability.
Out of six original scientific instruments aboard Akatsuki, four remained functional until the spacecraft lost contact in May 2024 after about a month of communication issues. The mission produced at least 178 scientific papers, contributing valuable insights into Venus’ atmosphere. Among its notable findings was the detection of a bow-shaped atmospheric feature that persisted for several days, likely caused by Venusian mountains generating gravity waves that push gases higher into the atmosphere. Understanding such phenomena sheds light on atmospheric dynamics that differ significantly from Earth.
With Akatsuki now silent, future Venus exploration depends on upcoming missions. NASA is developing DAVINCI and VERITAS, planned to study the planet’s atmosphere and surface, respectively, while the European Space Agency is preparing the EnVision orbiter mission. However, the continuation of some of these projects faces uncertainty due to budget cuts proposed in the 2026 NASA funding request, which has stirred political debate amid the ongoing U.S. government shutdown starting October 1, 2024. Despite these challenges, the legacy of Akatsuki highlights the enduring human curiosity about our neighboring planet and the technological creativity needed to explore such harsh environments.
