Abstract
Several lines of evidence support the presence of liquid water on Mars at different times. Among those, hydrated minerals testify to past aqueous weathering processes that can be precisely studied in Martian meteorites such as NWA 7533/7034. Bringing constraints on the timing of weathering of the Martian crust would help understand its evolution, the availability of liquid water, and the habitability of Mars. Here we present a new method based on U–Th–Pb isotope systems to assess if zircon crystals underwent low-temperature aqueous alteration, such as exemplified by Hadean-aged detrital crystals from Western Australia. Data for NWA 7533 zircons show evidence for aqueous alteration and modeling of U–Th–Pb isotope system evolution indicates that the latest alteration event occurred during the late Amazonian (227–56 Ma). This finding largely expands the time duration over which liquid water was available near the Martian surface, thereby suggesting that Mars might still be habitable.
Highlights
Several lines of evidence support the presence of liquid water on Mars at different times
An important aspect to consider when one wants to assess the sensitivity of zircon to chemical modifications and/or isotopic resetting is the preservation of its lattice
We developed a two-stage model of U–Th–Pb isotope evolution to test if an alteration event that occurred at 1500 or 1700 Ma can account for the observed decoupling between measured and timeintegrated Th/U (Fig. 5), and, that of zircon alteration in NWA 7533
Summary
Several lines of evidence support the presence of liquid water on Mars at different times. The increase of amorphization induces lattice expansion[6,10], which results in the formation of cracks in zircon[10,11] This effect enhances zircon’s sensitivity to thermal events and external fluid infiltrations as evidenced by modification of O isotope signatures[12,13], discordance of U–Pb ages[10,13,14], and enrichment in non-formula elements (e.g., Ca, Al, K, Fe)[15]. Pidgeon et al.[13] concluded that aqueous solutions infiltrated within zircons through cracks and into amorphous domains, which resulted in local modifications of O isotope signatures, deposition of OH radicals and increase of U and Th concentrations These features were essentially detected once analytical spots overlapped fractures. The term decoupling is not referred to as a mechanism but merely used to describe the fact that measured and time-integrated Th/U are different
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
