2001 Mars Odyssey is a spacecraft that orbits (as one might expect) Mars, launched (again, as one might expect) by NASA in 2001. Over a decade and a half later, it is still active, continuing to send data from the Martian orbit. This is old news.

The spacecraft’s biggest achievement was confirming the long-suspected presence of water ice on Mars. The evidence for this was first collected in 2002, and was confirmed in 2008 by Phoenix, a different spacecraft that landed on Mars. This is also old news.

So, then, if it is all old news, why am I talking about it? The data from Mars Odyssey, some of which was collected way back in the early 2000s, is still being analyzed today, long after its launch. In fact, earlier this week, through reanalyzing old data, scientists at Johns Hopkins University discovered further traces of water ice, this time around the Martian equator. They aren’t sure that it is actually water, as Mars Odyssey can’t directly detect water, but the probe did seem to observe high amounts of hydrogen, which has been proven to correspond with the existence of water.

This is significant because, previously, water ice was believed to be unable to exist at the equator, and had only been seen at higher latitudes, such as around the poles. The climate at the equator has long been considered too unstable for ice to have existed for hundreds of millions of years. If these scientists’ suggestions are true and there is indeed ice there, much of what we think we know about ice on Mars is called into question.

There are some speculative theories on how water ice could exist at the equator. One suggests that the Martian atmosphere cycled ice from the poles. Another suggests that the detected water is actually hydrated materials under the surface. None of these, however, explain how ice could have survived there for hundreds of millions of years.

The potential of water ice existing at the equator is also a big deal for possible human attempts to settle the planet. Human settlers would need a source of water in order to survive, and certainly water ice would be a convenient source. Conventional thinking has always held that this water source would be the polar ice cap or something near it, but water closer to the equator opens up loads of new possibilities.

All this is a reminder that some of what we consider special about Earth might even have analogues within our own solar system. And it’s also a reminder of how surprising, and promising, Mars can be.