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Multispectral Observations of Float Rocks Used to Investigate the Origin of Boulders on the Western Jezero Fan Front, Mars.

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Title: Multispectral Observations of Float Rocks Used to Investigate the Origin of Boulders on the Western Jezero Fan Front, Mars.
Authors: Kathir, B. S.1,2 (AUTHOR) bavani.s.kathir.gr@dartmouth.edu, Rice, M. S.1 (AUTHOR), Horgan, B. H. N.3 (AUTHOR), Mandon, L.4 (AUTHOR), Johnson, J. R.5 (AUTHOR), Stack, K. M.6 (AUTHOR), Broz, A. P.3 (AUTHOR), Williams, N.6 (AUTHOR), Mangold, N.7 (AUTHOR), Wiens, R. C.3 (AUTHOR), Simon, J. I.8 (AUTHOR), Bedford, C. C.3 (AUTHOR), Bechtold, A.9 (AUTHOR), Garczynski, B. J.1 (AUTHOR), Vaughan, A.10 (AUTHOR), Randazzo, N.11 (AUTHOR), Yingst, R. A.12 (AUTHOR), Theuer, S. A.1 (AUTHOR), Paar, G.13 (AUTHOR), Martínez‐Frías, J.14 (AUTHOR)
Source: Journal of Geophysical Research. Planets. Jun2025, Vol. 130 Issue 6, p1-29. 29p.
Subject Terms: Igneous rocks, Sedimentary rocks, Outcrops (Geology), Bedrock, Petrology
Abstract: In Jezero crater, Mars, the Perseverance rover has explored the western fan and encountered loose pieces of rock separated from outcrops or "float" rocks. Comparing float rocks to in‐place outcrops can provide key insights into the crater's erosional history and the diversity of units in the Jezero watershed that Perseverance cannot visit in situ. Here, we used multispectral observations from Perseverance's Mastcam‐Z instrument to investigate the lithology and origin of float rocks found on the western Jezero fan front (sols 415–707). We identified four textural classes of float rocks (conglomerates, layered, massive, and light‐toned) and investigated their physical characteristics, spectral properties, and distribution to interpret their source and mode of transport. Likely derived from local sedimentary fan outcrops, conglomerate and layered float rocks are highly spectrally variable and altered with differing ferric and ferrous signatures. Massive float rocks are the least altered with ferrous signatures and likely derived from local outcrop sources or more distal sources (∼50–250 km) in the Jezero watershed. Massive float rocks separate into two subclasses: massive olivine and massive pyroxene, which are likely derived from the regional olivine‐carbonate‐bearing watershed unit and the crustal Noachian basement unit, respectively. The unique light‐toned float rocks have variable hydration and low Fe‐abundance, but there is no local outcrop equivalent of these rocks on the crater floor or fan front, suggesting transport into the basin from a source region outside Jezero. Perseverance found no meteorites at the western fan, implying that fan sediments may be in the youngest ages estimated from crater counts (Hesperian). Plain Language Summary: The Mars 2020 Perseverance rover encountered many loose pieces of rocks not attached to outcrops at the front of the western fan in Jezero crater, Mars. As these rocks are not embedded in bedrock and thus "float" on land surfaces, they are known as float rocks. Float rocks have been removed from their original location and transported by fluvial, glacial, or impact processes on Mars. Using landscape images and visible to near‐infrared spectroscopy, we identified four types of float rocks: conglomerates, layered, massive, and light‐toned. We found that conglomerate and layered float rocks are sedimentary rocks that most likely eroded from the western fan. We interpreted the massive float rocks as igneous rocks transported from olivine‐ and low‐Ca pyroxene mineral‐rich units outside Jezero crater, which the latter are old Martian crustal rocks. The source of light‐toned float rocks is difficult to determine, as they have no similar physical or chemical characteristics to any local outcrops in Jezero crater that Perseverance has observed so far. Overall, studying these float rocks reveals how Jezero has eroded over time. Collecting samples of these massive boulder rocks from the ancient crust can help answer important questions about the past habitability of early Mars. Key Points: Conglomerate and layered float rocks most likely eroded from the western fan, but the origin of light‐toned float rocks is enigmaticMassive float rocks are igneous and were likely transported from olivine and low‐Ca pyroxene‐rich watershed units outside Jezero craterNo meteorites were discovered at the western Jezero fan front, implying that the fan sediments may be among the youngest ages predicted [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Planets is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Multispectral Observations of Float Rocks Used to Investigate the Origin of Boulders on the Western Jezero Fan Front, Mars.
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Planets%22">Journal of Geophysical Research. Planets</searchLink>. Jun2025, Vol. 130 Issue 6, p1-29. 29p.
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  Data: In Jezero crater, Mars, the Perseverance rover has explored the western fan and encountered loose pieces of rock separated from outcrops or "float" rocks. Comparing float rocks to in‐place outcrops can provide key insights into the crater's erosional history and the diversity of units in the Jezero watershed that Perseverance cannot visit in situ. Here, we used multispectral observations from Perseverance's Mastcam‐Z instrument to investigate the lithology and origin of float rocks found on the western Jezero fan front (sols 415–707). We identified four textural classes of float rocks (conglomerates, layered, massive, and light‐toned) and investigated their physical characteristics, spectral properties, and distribution to interpret their source and mode of transport. Likely derived from local sedimentary fan outcrops, conglomerate and layered float rocks are highly spectrally variable and altered with differing ferric and ferrous signatures. Massive float rocks are the least altered with ferrous signatures and likely derived from local outcrop sources or more distal sources (∼50–250 km) in the Jezero watershed. Massive float rocks separate into two subclasses: massive olivine and massive pyroxene, which are likely derived from the regional olivine‐carbonate‐bearing watershed unit and the crustal Noachian basement unit, respectively. The unique light‐toned float rocks have variable hydration and low Fe‐abundance, but there is no local outcrop equivalent of these rocks on the crater floor or fan front, suggesting transport into the basin from a source region outside Jezero. Perseverance found no meteorites at the western fan, implying that fan sediments may be in the youngest ages estimated from crater counts (Hesperian). Plain Language Summary: The Mars 2020 Perseverance rover encountered many loose pieces of rocks not attached to outcrops at the front of the western fan in Jezero crater, Mars. As these rocks are not embedded in bedrock and thus "float" on land surfaces, they are known as float rocks. Float rocks have been removed from their original location and transported by fluvial, glacial, or impact processes on Mars. Using landscape images and visible to near‐infrared spectroscopy, we identified four types of float rocks: conglomerates, layered, massive, and light‐toned. We found that conglomerate and layered float rocks are sedimentary rocks that most likely eroded from the western fan. We interpreted the massive float rocks as igneous rocks transported from olivine‐ and low‐Ca pyroxene mineral‐rich units outside Jezero crater, which the latter are old Martian crustal rocks. The source of light‐toned float rocks is difficult to determine, as they have no similar physical or chemical characteristics to any local outcrops in Jezero crater that Perseverance has observed so far. Overall, studying these float rocks reveals how Jezero has eroded over time. Collecting samples of these massive boulder rocks from the ancient crust can help answer important questions about the past habitability of early Mars. Key Points: Conglomerate and layered float rocks most likely eroded from the western fan, but the origin of light‐toned float rocks is enigmaticMassive float rocks are igneous and were likely transported from olivine and low‐Ca pyroxene‐rich watershed units outside Jezero craterNo meteorites were discovered at the western Jezero fan front, implying that the fan sediments may be among the youngest ages predicted [ABSTRACT FROM AUTHOR]
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  Data: <i>Copyright of Journal of Geophysical Research. Planets is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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