One of the major scientific achievements of the lunar sample return missions (Apollo, Luna, Chang’e) was the establishment of a chronology model enabling the age of surfaces to be deduced from the observed crater density. This model is currently the only available tool for dating the surfaces of the Solar System, enabling us to pinpoint the timing of the major events responsible for their geological evolution. Most chronology models assume a homogeneous cratering rate across the entire lunar surface.
However, the synchronicity of the lunar orbit around the Earth and the orbital distribution of impactors call into question the hypothesis of a homogeneous lunar impact flow. What are the intensity and consequences of impact flux heterogeneity on lunar surface age measurements ? This is precisely what an international research team, in which IMCCE is involved, has just established.
Scientists have discovered that the rate of cratering on the Moon varies by a factor of 1.8 between different regions. What does this mean for the interpretation of lunar samples ? The regions from which these rocks originated would not have recorded the same impact rate, and the chronology systems for the bodies of the Solar System would be in error. The researchers then used this variation in cratering rate to recalibrate the lunar chronology. This new model modifies by up to 30% the age of lunar surfaces deduced from crater counts over decades. As a result, our vision of the temporality of the Moon’s geological activity could be revised, as could the chronologies of other planetary bodies such as Mercury and Mars, which are calibrated to that of the Moon. Finally, future lunar sampling missions such as Artemis or Chang’e-6 will enable us to refine this chronology for the earliest periods, over 3.5 billion years ago.
CNRS laboratories involved
- Centre européen de recherche et d’enseignement de géosciences de l’environnement (CEREGE - OSU Pythéas)
- Tutelles : AMU / CNRS / IRD / INRAE / Collège de France
- Laboratoire d’astrophysique de Marseille (LAM - OSU Pythéas)
- Tutelles : CNRS / CNES / AMU
- Institut de mécanique céleste et de calcul des éphémérides (IMCCE - OBS Paris)
- Tutelles : CNRS / Observatoire de Paris - PSL
Know more
Anthony Lagain, Hadrien A.R. Devillepoix, Pierre Vernazza, Darrel Robertson, Mikael Granvik, Petr Pokorny, Anthony Ozerov, Patrick M. Shober, Laurent Jorda, Konstantinos Servis, John H. Fairweather, Yoann Quesnel, Gretchen K. Benedix, Recalibration of the lunar chronology due to spatial cratering-rate variability,
Icarus, Volume 411, 2024.