NASA's Curiosity rover at Windjana drilling site, where Mn-enrichments are found. (Image credit: NASA/JPL-Caltech/MSSS)
● Molecular oxygen (O2) is a key molecule in the habitability of Mars because it can both provide life with energy and be generated by life (i.e., photosynthesis) on Earth.
● The experimental results suggest that the Mn oxides on Mars found by NASA's Mars rovers are highly oxidizing manganese dioxide (MnO2), requiring high levels of O2 at that time.
● The atmospheric O2 would have been comparable to that of Earth's atmosphere after the emergence of O2-producing photosynthesis.
NASA's Mars rovers Curiosity and Opportunity found manganese (Mn)-rich veins with trace metal enrichments within ancient sediments on early Mars. Although the previous studies showed that the Mn enrichments were caused by deposition of Mn oxides within ancient groundwater, the redox states of the aqueous environments are poorly constrained.
From the laboratory experiments that the Mn oxides found on Mars are manganese dioxide, which explains the enrichments of trace metals and suggests there were highly oxidizing aqueous environments on early Mars. To form MnO2, atmospheric O2 levels would need to be as high as those of early Earth's atmosphere after the rise of O2 due to O2-producung photosynthesis. The atmospheric O2 might have been important for the habitability of early Mars since it can provide chemical energy to chemoautotrophic life.
||Journal of Geophysical Research - Planets
|Title of the paper
||Highly oxidizing aqueous environments on early Mars inferred from scavenging pattern of trace metals on manganese oxides
||Natsumi Noda1,2*, Shoko Imamura1,2*, Yasuhito Sekine1,* †, Minako Kurisu2, Keisuke Fukushi3, Naoki Terada4, Soichiro Uesugi2, Chiya Numako5, Yoshio Takahashi2, Jens Hartmann6
*These authors equally contributed to this work.
||1Earth-Life Science Institute, Tokyo Institute of Technology
2Department of Earth and Planetary Science, University of Tokyo
3Institute of Nature and Environmental Technology, Kanazawa University
4Department of Geophysics, Tohoku University
5Graduate School of Science, Chiba University
6Institute for Geology, Center for Earth System Research and Sustainability, Universität Hamburg
|Online published date
||16 April 2019