For nearly a month, NASA has been scrambling to make contact with a spacecraft in orbit around Mars that abruptly fell silent.

The space agency lost communication with the MAVEN probe (short for Mars Atmosphere and Volatile EvolutioN) on Dec. 6, and efforts to re-establish a connection have been futile. Based on bits of data received that day, mission controllers think the probe was spinning unexpectedly.

NASA now has to wait until Jan. 16 before it can again try to revive MAVEN, because Mars and Earth have been on opposite sides of the sun since Monday, resulting in a prolonged communications blackout.

Overall, it’s not looking promising for one of NASA’s workhorse missions.

Since the MAVEN spacecraft entered orbit around Mars in 2014, it has been studying the red planet’s upper atmosphere, including a plasma layer known as the ionosphere, and investigating how and why Mars has been losing its atmosphere over billions of years. The spacecraft has also been instrumental in relaying communications between two rovers on the surface of Mars, Curiosity and Perseverance, and Earth.

NASA hasn’t been able to reach MAVEN since it experienced what the agency called a “loss of signal” with ground stations on Earth on Dec. 6. At the time, the spacecraft was orbiting behind Mars, so the signal loss was routine and expected, as Mars always blocks MAVEN from phoning home during the maneuver. This time, however, when the probe re-emerged from behind the red planet, NASA could not pick up any signals from it.

NASA said it was “investigating the anomaly” in a statement on Dec. 9 but provided few details. Mission controllers reported that all of MAVEN’s subsystems had been working normally before it passed behind Mars.

In an update about a week later, NASA said no transmissions had been received from MAVEN since Dec. 4, but that engineers had recovered a brief fragment of tracking data from Dec. 6.

What they found was troubling: “Analysis of that signal suggests that the MAVEN spacecraft was rotating in an unexpected manner when it emerged from behind Mars,” NASA officials said in a statement.

The space agency has been using a global array of giant radio antennas, known as the Deep Space Network, to send commands to MAVEN and monitor for any incoming signals. On Dec. 16 and 20, NASA tried snapping photos of MAVEN in orbit from the surface of Mars, using an instrument aboard the agency’s Curiosity rover.

At the same time, mission controllers are closely analyzing the last fragments of tracking data recovered. NASA said on Dec. 23 that it was attempting to piece together a timeline of events to figure out what went wrong. NASA did not provide additional details in a request for comment and referred NBC News to the agency’s update on Dec. 23.

The MAVEN mission was originally designed to last just two years, but it has been operating continuously for more than a decade. In 2024, NASA celebrated the probe’s 10th anniversary orbiting Mars.

By studying the process of atmospheric loss on Mars, MAVEN was helping scientists get a clearer picture of the planet’s past and present climate and how it transformed from a potentially habitable world with liquid water on its surface to the cold and barren planet that it is today.

The spacecraft is one of three that NASA currently has in orbit around Mars. The space agency also operates the Mars Reconnaissance Orbiter, which launched in 2005, and Mars Odyssey, which lifted off in 2001.

This article was originally published on NBCNews.com