A meteorite found in the Malian Sahara preserves a fragment of Mars’s earliest history. Named Teghaza 001, the rock gives researchers clues about the Red Planet’s crust and the ancient action of water. Its age and minerals shed light on a period that Earth’s rocks, often erased by erosion and tectonics, do not document well.
An age recorded in tiny crystals
Prospectors discovered Teghaza 001 in 2022, on the Teghaza salt flat. The stone weighs about 800 grams. Its Martian origin was established in part from its oxygen isotopes, whose proportions match those of other rocks from Mars.
The study, published in the journal “Science” on 29 October, focused on zircon grains found in the meteorite. These crystals incorporate uranium as they form. Over time, it turns into lead at a known rate: measuring both elements therefore makes it possible to estimate the age of the crystal and, in this case, of the rock that contains it.
Uranium-lead dating puts the zircons at about 4.11 billion years old. A second analysis, measuring rubidium and strontium in a tiny fragment, gives an age of about 4.24 billion years, with less precision. These results should not be read as two perfectly equivalent dates: they converge on an extremely ancient rock, formed at least 4.1 billion years ago.
This sets Teghaza 001 apart from many known Martian meteorites, which formed much more recently. Comparison with Black Beauty, a meteorite made up of several types of rock, also helps explain its significance: Teghaza 001 is described as a single type of rock, offering a more direct sample of ancient Martian crustal material.
A rock formed before being altered by water
The age at which the rock formed is not the age of all the transformations it underwent. Analyses indicate that groundwater altered its minerals about 4.1 billion years ago. The rock therefore already existed when it interacted with these fluids; it may have formed even earlier, from cooled magma.
The oxygen isotopes, textures and mineral composition make this interaction particularly interesting. They suggest that water circulated through the Martian crust early in the planet’s history. This finding contributes to the study of a planet that did not always look as cold and arid as it does today, but on its own it does not describe the climate of the entire planet or the duration of any potentially wet environment.
The presence of minerals associated with alteration by fluids indicates a geological context, not the past presence of life. Some substances, such as the manganese oxides reported in the sample, may interest researchers studying potentially habitable environments. They are not, in themselves, biological evidence.
Tracing it back to a region of Mars
A Martian meteorite was ejected from its home planet by an impact, travelled through space before falling to Earth, and was then found and studied. For Teghaza 001, researchers do not yet know the precise location of the original impact or the date it fell in the Sahara.
They compared its composition with observations made by spacecraft that have studied Mars from a distance or on its surface: the Mars Reconnaissance Orbiter and the Viking landers, as well as the Curiosity and Perseverance rovers. The matches point towards the cratered highlands of the southern hemisphere. The study proposes thirteen possible sites, rather than identifying a definitive point of origin.
This lead matters because the available Martian samples do not necessarily represent the planet’s full diversity. If the proposed origin is confirmed, the meteorite could come from an ancient region still poorly represented in the rocks studied on Earth. Orbital data narrow down the possibilities, but they cannot replace direct analysis of the terrain of origin.
What this rock can contribute
On Earth, rocks more than 3.8 billion years old are rare: erosion, volcanism and the movement of tectonic plates have altered or destroyed much of the ancient record. Mars therefore offers another setting in which to study the earliest stages of planetary evolution. Meteorites provide fragments of it, while future missions could study samples collected on site.
Teghaza 001 nevertheless remains a single sample, not a complete map of early Mars. Its study has only just begun, and future analyses may clarify the sequence of events: the rock’s formation, the circulation of fluids, and then its ejection into space. Its contribution lies in this mineral window onto an ancient crust altered by water, and in the questions it helps raise about terrains that future missions could explore.
References
- University of New Mexico: study of Teghaza 001 and analyses of the meteorite
- Clubic: overview of its age, minerals and clues to its Martian origin
A slice of Teghaza 001 viewed under reflected light to identify the minerals to be analysed.
Credit: NASA/JPL-Caltech — Wikimedia Commons — Public domain.
