As it passed behind Mars six months ago, NASA's MAVEN probe was still working normally, studying how the solar wind impacts the Martian atmosphere. But during that 20- to 30-minute pass behind the red planet, out of contact with Earth, something went wrong, and the spacecraft has not been heard from since. 

On Wednesday, after concerted efforts to remotely reset the spacecraft's computer and prompt the probe to "phone home," agency officials said the $582 million orbiter could not be recovered and that its extraordinarily successful mission was at an end.  

"Our last successful communication with MAVEN occurred on December 6 of 2025," said Mike Moreau, MAVEN project manager at NASA's Goddard Space Flight Center in Maryland. "The MAVEN spacecraft and all of the subsystems were nominal when the spacecraft entered a normally scheduled occultation where the spacecraft passed behind Mars." 

"There were no indications of problems with the spacecraft in the week prior to the loss of signal, but when the spacecraft emerged behind Mars on December 6, the Deep Space Network did not detect a signal," Moreau said.

Commands were sent in the blind in an attempt to force MAVEN's flight computer to restart, but to no avail. 

"Unfortunately, all of these efforts to reestablish communication with MAVEN were ultimately unsuccessful, and no telemetry or signal has been received from the spacecraft since December 6," Moreau said. 

Launched on Nov. 18, 2013, MAVEN, an acronym standing for the Mars Atmosphere and Volatile Evolution Mission, braked into orbit around Mars the following September. 

Equipped with a sophisticated suite of instruments, the probe was designed to study the Martian atmosphere to learn more about how it is eroded, or blown away and thinned out by particles in the solar wind.

Originally designed to operate for just one year around Mars, MAVEN's mission was repeatedly extended, enabling the most extensive research into the workings of the Martian atmosphere ever attempted.

Mars was once a warmer, wetter world, but for water to exist on the surface, a much higher atmospheric pressure is required than what is present today. MAVEN has provided major insights into how charged particles in the solar wind have eroded the Martian atmosphere over billions of years. 

"One of our most exciting discoveries used 11 years of MAVEN data to observe, for the first time in any planet, an atmospheric escape process called 'sputtering,'" said Shannon Curry, the principal investigator at the University of Colorado at Boulder.

"This is where charged particles crash into the upper atmosphere and splash out the neutral atmosphere, much like doing a cannonball in a pool," Curry said. "Our team (confirmed) that this process has been a dominant escape mechanism for billions of years, which has incredible implications for other planets in our solar system and even exoplanets." 

Along with studying the red planet's atmosphere, MAVEN also helped relay signals from NASA's two operational Mars rovers, Curiosity and Perseverance, to flight controllers at the Jet Propulsion Laboratory. Three other Mars orbiters provide similar communications relay service.

While MAVEN operated well beyond its initial mission, NASA is attempting to find out what might have gone wrong in case there are lessons to be learned for other missions. In February, the agency set up an anomaly review board to look for the root cause.

As part of that ongoing investigation, engineers re-analyzed recordings of what the Deep Space Network possibly could have "heard" when MAVEN emerged from behind Mars as part of an ongoing radio science experiment. As expected, normal telemetry was not there, but they found fragments of data indicating the spacecraft was rotating at 2.7 revolutions per minute.

Other than periodically changing its orientation as required for science observations, communications and power generation, MAVEN did not normally rotate, keeping its solar panels aimed toward the sun and its antenna pointed toward Earth.

At the observed rotation rate, normal communications likely would not have been possible, and the arrays would have been unable to generate sufficient power. In that scenario, the probe's batteries would have quickly drained. 

Moreau would not speculate on what might have happened while the spacecraft was out of contact with Earth, saying he was eager to hear the results of the ongoing investigation. 

Whatever the cause, the rotation rate observed in the recovered telemetry was not survivable. The spacecraft is expected to remain in the same orbit around Mars for at least the next 50 to 100 years, but NASA will make no additional attempts to regain contact.

"On a personal note, leading this team has been a privilege and an honor," Curry said. "This team has worked tirelessly on operating the spacecraft and delivering exceptional science. It's their vision, their drive and their curiosity that brought these amazing discoveries into fruition. I will miss the spacecraft and this team dearly." 

Asked by a reporter what should go on MAVEN's tombstone, Curry said: "Best Mars mission ever."