Mars Atmosphere and Volatile Evolution Mission is a NASA spacecraft that has been in orbit around our neighboring planet since September 2014 and it completed 1,000 days of exploring the red planet’s upper atmosphere Saturday. The primary objective of MAVEN is to understand how the loss of most of its atmosphere caused changes to Martian climate over time.

“MAVEN has made tremendous discoveries about the Mars upper atmosphere and how it interacts with the sun and the solar wind. These are allowing us to understand not just the behavior of the atmosphere today, but how the atmosphere has changed through time,” Bruce Jakosky, MAVEN principal investigator from the University of Colorado, Boulder, said in a statement Saturday.

The spacecraft has now completed about one-and-a-half Martian years (one year on Mars is 687 Earth days) of observation, and from all the scientific data it has collected about Mars’ atmosphere, here is a list of the top discoveries — some of them quite unexpected — according to NASA.

Read: Mars Atmosphere Has Metal, NASA’s MAVEN Finds

1. Mars was wetter and warmer than today, but that changed after most of its atmosphere was stripped away by the sun and solar winds.

2. Measurements by MAVEN — of the rate at which the upper atmosphere loses gas today, as well as isotopes in the region — suggest almost two-thirds of the atmosphere’s gas has been lost to space forever.

3. The amount of hydrogen in the upper atmosphere varies by a factor of 10 during different seasons through the Martian year. The hydrogen comes from the lower atmosphere, where sunlight breaks up water into hydrogen and oxygen. However, the seasonal variation is both unexpected and not well understood.

4. The exchange of gases between the lower and upper atmosphere also causes unexpected and complex behavior in the distribution of ozone and nitric oxide, which has been imaged by MAVEN. The dynamic process of the gas exchange is not yet understood.

5. The ionosphere around Mars has an always-present layer of charged metal atoms, and its detection was the first instance of a charged layer being found around a planet other than Earth (though scientists think they exist around other planets in the solar system too).

6. The ionosphere does not disperse some particles from the solar wind, which manage to penetrate unexpectedly deep into the upper atmosphere. This is possible because chemical reactions in the ionosphere turned charged particles of the solar wind into neutral particles, which then penetrate deep into the atmosphere.

Read: NASA’s MAVEN Sheds Light On Mars Moon Phobos

7. In the absence of an intrinsic global magnetic field, small regions of the Martian surface that have a magnetized crust interact with the incoming solar wind on regional scales, creating a magnetosphere that varies on short timescales and appears “lumpy.”

8. MAVEN found two new types of auroras on Mars — termed “diffuse” and “proton” — that are caused by very different processes from the magnetic field interactions on Earth. They are caused by solar particles that stream into the Martian atmosphere following ejection by different types of solar storms.

“We’re excited that MAVEN is continuing its observations. It’s now observing a second Martian year, and looking at the ways that the seasonal cycles and the solar cycle affect the system,” Gina DiBraccio, MAVEN project scientist from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in the statement.