Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001
Open accessAbstract
Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest that the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and Fe-sulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features, including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
Most ALH 84001 globules had only a single magnetite rim, whereas some contained a white magnesite zone between two outer rims of magnetite.
“Whereas some globules contained a white magnesite zone between two outer rims of magnetite-as identified from previous observations (McKay et al. 1996) and during Raman mapping-most had only a single magnetite rim”
From Comprehensive imaging and Raman spectroscopy of carbonate globules from Martian meteorite ALH 84001 and a terrestrial analogue from Svalbard (2007) · cites this paper as McKay et al. 1996
Hematite may not have been detected previously in ALH 84001 globules because the primary analytical tools were optical and electron microscopy and elemental mapping, with the mineralogy of the carbonate composition being inferred from assessments based on the amounts of Fe, Ca, Mg, Mn, C, and O present.
“Hematite may not have been detected previously in ALH 84001 globules because the primary analytical tools were optical and electron microscopy and elemental mapping (electron microprobe, energy dispersive X-ray analysis), with the mineralogy of the carbonate composition being inferred from assessments based on the amounts of Fe, Ca, Mg, Mn, C, and O present (McKay et al. 1996;Mittlefehldt 1994aM”
From Comprehensive imaging and Raman spectroscopy of carbonate globules from Martian meteorite ALH 84001 and a terrestrial analogue from Svalbard (2007) · cites this paper as McKay et al. 1996
Two types of carbonate globules have previously been described in ALH 84001: dark brown globules containing a single magnetite rim, and lighter orange-colored globules with a second magnetite outer rim bounded by an area of magnesite.
“Two types of carbonate globules (Fig. 1) have previously been described in ALH 84001: dark brown globules containing a single magnetite rim, and lighter orange-colored globules with a second magnetite outer rim bounded by an area of magnesite (e.g., Figs.1a and 1d) (McKay et al. 1996;Treiman et al. 2003).”
From Comprehensive imaging and Raman spectroscopy of carbonate globules from Martian meteorite ALH 84001 and a terrestrial analogue from Svalbard (2007) · cites this paper as McKay et al. 1996
Iron- and magnesium-rich carbonate globules (with calcium-rich areas) are the host minerals of the microscopic structures in question within the meteorite ALH84001.
“Particular interest has focused on the ability to identify carbonate minerals on Mars' surface because iron- and magnesium-rich carbonate globules (with calcium-rich areas) are the host minerals of the microscopic structures in question within the meteorite.”
From Thermal infrared emission spectroscopy of anhydrous carbonates (1997) · cites this paper as McKay et al., 1996
Carbonate has been identified in the Martian meteorite ALH84001.
“Not only has carbonate been identified in the Martian meteorite ALH84001 [McKay et al., 1996]”
From Thermal infrared emission spectroscopy of anhydrous carbonates (1997) · cites this paper as McKay et al., 1996
No citation lists for this paper
No citation lists for this paper yet — checked again daily.
References 61 · Cited by 1,883
- Authors
- McKay, D. S., Gibson, E. K., Thomas-Keprta, K. L., Vali, H., Romanek, C. S., Clemett, S. J., Chillier, X. D. F., Maechling, C. R., & Zare, R. N.
- Affiliations
- National Aeronautics and Space Administration (US)
- Johnson Space Center (US)
- Lockheed Martin (United States) (US)
- McGill University (CA)
- University of Georgia (US)
- Stanford University (US)
- Venue
- Science
- Published
- 1996-08-16
- Volume
- 273
- Issue
- 5277
- Pages
- 924-930
- ISSN
- 0036-8075 (ISSN-L)
- 1095-9203
- OpenAlex
- W1968713120
- Cited by
- 1,883
- References
- 61
- Citations by year
- 2026: 34 · 2025: 35 · 2024: 37 · 2023: 51 · 2022: 45 · 2021: 78 · 2020: 48 · 2019: 70 · 2018: 91 · 2017: 33 · 2016: 45 · 2015: 46 · 2014: 43 · 2013: 56 · 2012: 68
- FWCI
- 95.99
- Type
- journal article
- Language
- en
- Open access
- Licence
- cc-by
- Locations
- Science (publishedVersion)
- PubMed (publishedVersion)
- Archive ouverte UNIGE (University of Geneva) (submittedVersion, cc-by)
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Planetary Science and Exploration
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astro and Planetary Science
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Space Science and Extraterrestrial Life
- Keywords
- ALH84001, Martian meteorites, polycyclic aromatic hydrocarbons, carbonate globules, magnetite, iron sulfide, bacterial carbonate precipitation, fracture morphology
- MeSH terms
- Antarctic Regions, Bacteria, Carbonates, Extraterrestrial Environment, Ferrous Compounds, Fossils, Hydrogen-Ion Concentration, Iron, Microscopy, Electron, Microscopy, Electron, Scanning, Oxides, Polycyclic Aromatic Hydrocarbons, Mars, Exobiology, Meteoroids, Ferrosoferric Oxide
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review
