In their early history, Earth and Mars were strikingly similar. Around four billion years ago, both planets boasted vast, warm seas. However, while Earth managed to preserve its oceans, Mars saw its waters either evaporate into space or freeze beneath its dusty surface. The reason for this stark divergence remains unclear, though it may be tied to the origins of their water.
Geological studies show that Earth’s water cycle likely stabilized early, with liquid water present continuously from about 4.5 billion years ago to the present.
In contrast, the history of water on Mars is more elusive. Clay minerals, which cover about 45% of the Martian surface, date back to the Noachian period (4.1 to 3.7 billion years ago), suggesting the presence of water during that time. Evidence of water flows also appears in the Hesperian period (3.7 to 3.0 billion years ago). However, during the Amazonian period (3 billion years ago to today), Mars appears to have been largely dry.
The pre-Noachian era, the earliest period of Mars’ history, remains mostly a mystery. A new study, however, sheds light on this ancient epoch, drawing insights from a Martian meteorite known as Black Beauty.
There are around 200 meteorites known to have originated from Mars, and these are currently the only physical samples of the planet available on Earth. One of the largest, Northwest Africa 7034, discovered in Western Sahara in 2011, is nicknamed “Black Beauty” due to its striking black color. Composed of material about 4.4 billion years old, it also contains more water than any other Martian meteorite. However, since Black Beauty was ejected from Mars just 1.5 billion years ago, it remains unclear whether it formed in a wet environment or if it acquired its water during the Noachian or Hesperian periods.
The new study focuses not on the meteorite itself, but on small zircon crystals embedded within it. These crystals, dated to 4.48–4.43 billion years ago, formed during the Pre-Noachian period. Remarkably, the crystals display layers of iron, aluminum, and sodium in a pattern known as oscillatory zoning. This kind of banding, typically seen in Earth’s hydrothermal geysers, is rare in zircon crystals. The only place where this pattern is observed on Earth is in hydrothermal environments like those at Yellowstone National Park.
The discovery of these zircon crystals in Black Beauty provides compelling evidence that Mars was not only wet during the Pre-Noachian period, but also geologically active with warm thermal vents. On Earth, such vents are thought to have played a role in the origins of life. While the question of whether life ever existed on Mars remains unanswered, it is clear that the conditions necessary for life were present on Mars in its early history.
The study was published in the journal Science Advances.
