The era of continuous human presence at Venus has temporarily ended as the Japan Aerospace Exploration Agency (JAXA) officially declared its Akatsuki (meaning "Dawn") orbiter dead on October 28, 2025. This decision followed a sustained period of silence, with the Venus Climate Orbiter failing to respond to calls from mission control for over a year, having first lost contact on May 29, 2024.
Akatsuki, launched in 2010, was humanity's sole active presence orbiting the planet, making its operational termination a significant moment for solar system exploration.
A Mission of Perseverance and Discovery
Akatsuki's journey was characterized by both initial setback and ultimate triumph, a testament to engineering ingenuity:
Initial Failure: The spacecraft's first attempt to enter Venus orbit in December 2010 failed when a single valve on the main engine's fuel line malfunctioned, causing the probe to shoot past the planet and enter a five-year orbit around the Sun.
Ingenious Recovery: Instead of abandoning the mission, JAXA engineers devised a brilliant solution. In December 2015, they used the spacecraft's much less powerful attitude control thrusters—designed for fine adjustments—to perform a second, successful orbital insertion. This method had never been used before for such a maneuver.
Exceeding Expectations: Despite being designed for a 4.5-year lifetime, Akatsuki persisted in its study of Venus for nearly a decade, well exceeding its expected operational period.
Scientific Legacy: Unlocking the Venusian Climate
Akatsuki's primary goal was to investigate the extreme climate and weather phenomena of Venus, whose surface temperatures can melt lead and whose atmosphere is subject to crushing pressure. The mission was particularly focused on the planet's notorious "super-rotation," a phenomenon where the upper atmosphere whips around the entire planet in just four Earth days, about 60 times faster than the planet's slow rotation.
Key scientific contributions include:
Super-Rotation Mechanism: Akatsuki's steady gaze helped researchers map the clouds and measure their speed, suggesting that the super-rotation is maintained by solar heating as air is accelerated by the thermal input from the Sun.
Giant Atmospheric Structure: The orbiter discovered a giant curved structure in the atmosphere, stretching from one pole to the other, which scientists later determined was a stationary gravity wave caused by air currents flowing over Venus's mountainous regions.
Atmospheric Mapping: The probe provided the world's first data on how temperature varies with altitude across the entire planet, particularly in the cloud deck between 40 and 85 kilometers.
Instrument Lifespan: While two of its six cameras (infrared) stopped working about a year after orbital insertion, the remaining four instruments were believed to be healthy until communications were lost.
Akatsuki's discoveries, published in 178 journal papers and counting, have profoundly changed our view of Earth's "twin," providing crucial context for understanding how terrestrial planets evolve.
The End of an Era
The termination of the mission on September 18, 2025 (formally declared in late October 2025) leaves Venus temporarily unobserved by dedicated orbiters. However, the legacy of Akatsuki paves the way for a new generation of Venus missions, including NASA's DAVINCI and VERITAS probes, planned for the 2030s, which will build upon the groundbreaking work of JAXA's resilient spacecraft.