A study published online in Science on October 29, 2026, concludes that Martian meteorite Teghaza 001 formed no later than about 4.1 billion years ago. The researchers interpret water-related alteration around that age as hydrothermal activity that happened shortly after the rock first crystallized. Those dates describe related but distinct stages in the rock’s history. (Science study)
How researchers identified Teghaza 001 as Martian
Oxygen-isotope measurements support Teghaza 001’s Martian origin. The official Meteoritical Bulletin also lists pyroxene iron-to-manganese ratios and maskelynite composition among the classification evidence; it catalogs the specimen as a Martian shergottite. (Meteoritical Bulletin entry)
The meteorite was found in Mali’s Sahara in 2022. The eight recovered stones have a combined mass of 798.5 grams. The largest weighs 442 grams and measures about 10 centimeters across, so the often-rounded figure of about 800 grams describes the whole recovered set, not one stone. (Science study)
What the age measurements show
The study reports three isotope-dating results from different minerals or materials. Ma means million years ago; the reported uncertainties are two standard errors.
| Dating method | Reported age | Material and measurement note |
| Zircon U-Pb | 4,114 ± 17 Ma | Weighted mean from six concordant measurements |
| Zircon Pb-Pb | 4,113 ± 14 Ma | Weighted mean |
| In-situ Rb-Sr | 4,238 ± 208 Ma | Isochron for plagioclase, pyroxene and matrix |
The authors consider the three chronometers consistent with an age of about 4.1 billion years. Their conclusion is that the rock formed no later than approximately that time. The measurements use different isotope systems and materials, rather than giving three identical readings from one clock. (Science study)
Why the alteration date differs from the formation date
The researchers interpret sodium-rich alteration in zircon and plagioclase as evidence of hydrothermal activity around 4.1 billion years ago, shortly after primary crystallization. Hydrothermal alteration occurs when heated fluids change a rock’s minerals. In this case, altered minerals and oxygen-isotope evidence point to reactions with fluids enriched in oxygen-18 before an impact ejected the rock from Mars. (Science study)
That interpretation explains why the paper discusses both a formation-age conclusion and an alteration event around 4.1 billion years ago. The first describes when the rock had formed by; the second describes a later interaction with fluids in its early history.
A separate study published in Science Advances in June 2026 examined H₂O and deuterium-to-hydrogen (D/H) measurements in igneous calcium phosphates from Teghaza 001 to assess water reservoirs on early Mars. The two studies address different questions: one reports the meteorite’s age and alteration history, while the other focuses on water measurements. (Science Advances study)
The water-related findings describe interactions between water and rock. They do not report a detection of life on Mars.
The likely Martian source region
The study points to the Noachian southern highlands as Teghaza 001’s most likely source region, particularly an area northwest of the Hellas impact crater. That is a regional inference, not a specific landing site. (Science study)
A surface impact can eject Martian rock into space; material from Mars can then travel to Earth. NASA describes this process and the use of mineral and chemical comparisons to identify Martian meteorites. (NASA’s explanation of Martian meteorites)
