Last week NASA’s Messenger mission, to study the planet Mercury, came to an abrupt halt when the spacecraft finally ran out of fuel and crashed. However, data from the mission will continue to provide new information about Mercury for some time to come.

The latest discovery about the planet closest to the sun is that its magnetosphere is nearly 4 billion years old. The discovery provides new insight into the history of Mercury and the early history of our solar system.

The study, published in Science Express, uses data gathered in 2014 and 2015 during one of Messengers closest passes to Mercury. The spacecraft was within The spacecraft was within 10 miles of the planet when the data was acquired.

Scientists have known that Mercury had a weak magnetosphere for awhile. While it is not as strong as the Earth’s, it is thought to be the only other body in the inner solar system to have a magnetosphere. The magnetic field is generated by molten iron within the spinning core of the planet.

Mars is thought to have had a magnetosphere at one time, but it was lost at some point about 3 billion years ago. That roughly corresponds to the time when Mars is thought to have lost much of its water and atmosphere.

This presents a challenge for those hoping to “terraform” Mars. While it is possible to introduce more water and possibly microbial and plant life to the planet, there is no known way to reboot a magnetosphere.

The Earth’s magnetosphere blocks most of the solar wind and solar radiation. Without it the Earth would be much warmer, dryer and level of radiation would be much higher. Although Mercury also has a magnetosphere, its proximity to the sun makes it much to warm to support life, as we know it.

Being close to the sun also makes Mercury more of a target for asteroids and meteors. In addition to its heavily cratered surface, Mercury’s black color comes from a rain of cosmic dust, left by asteroids orbiting the sun over billions of years according to a report published in March.

Mercury’s magnetosphere could, however, help to explain how the planet has managed to retain small amounts of ice, despite the heat. In addition to providing data on Mercury’s magnetosphere, the messenger mission showed that the planet has ice at its poles as well as buried deep inside some of its craters.

Messenger lifted off in 2004 and began, what was supposed to be, a one year mission orbiting Mercury in 2011.

“The mission was originally planned to last one year; no one expected it to go for four. The science from these recent observations is really interesting and what we’ve learned about the magnetic field is just the first part of it,” said Catherine Johnson, a University of British Columbia planetary scientist and lead author of the study on Mercury’s magnetosphere in a statement.

Messengers data on rocks close to Mercury’s surface showed that the planets magnetic field is 3.7 to 3.9 billion years old. That means that the magnetosphere formed in the early history of the planet. Like Earth, Mercury is though to be roughly 4.5 billion years old.

“If we didn’t have these recent observations, we would never have known how Mercury’s magnetic field evolved over time. It’s just been waiting to tell us its story,” said Johnson, also a scientist at the Planetary Science Institute.