nanobe

{{Short description|Rock and sediment microstructure}}{{use dmy dates|date=July 2023}}

File:ALH84001 structures.jpg are similar to the structures found in nanobes]]

{{distinguish|Nanobacteria|Ultramicrobacteria}}

A nanobe ({{IPAc-en|ˈ|n|æ|n|oʊ|b|,_|ˈ|n|eɪ|n|oʊ|b}}){{cite dictionary |title=nanobe |dictionary=Lexico U.S. English Dictionary |publisher=Oxford University Press |url=http://www.lexico.com/en/definition/nanobe |url-status=dead |archive-url=https://web.archive.org/web/20190731214907/https://www.lexico.com/en/definition/nanobe |archive-date=July 31, 2019}} is a tiny filamental structure first found in some rocks and sediments. Some scientists hypothesize that nanobes are the smallest form of life, {{sfrac|1| 10 }} the size of the smallest known bacteria.{{cite journal | last = Nanjundiah | first = V. | year = 2000 | title = The smallest form of life yet? | journal = Journal of Biosciences | volume = 25 | issue = 1 | pages = 9–10 | url = http://eprints.iisc.ernet.in/archive/00001799/01/25smallest25(1)-9to10mar2000.pdf | doi = 10.1007/BF02985175 | pmid = 10824192 | s2cid = 29030837 }}

No conclusive evidence exists that these structures are, or are not, living organisms, so their classification is controversial.

The 1996 discovery of nanobes was published in 1998{{cite journal |author1=Uwins, Philippa J.R. |display-authors=etal |year=1998 |title=Novel nano-organisms from Australian sandstones |journal=American Mineralogist | volume=83 |issue=11-12 |pages=1541–1550, Part 2 |doi=10.2138/am-1998-11-1242

|bibcode=1998AmMin..83.1541U |url=http://www.microscopy-uk.org.uk/nanobes/nanobes.pdf }} by Uwins et al.,{{cite news |title=Nanobes: About Philippa Uwins and the discovery team |website=microscopy-uk.org.uk |url=http://www.microscopy-uk.org.uk/nanobes/nanophil.html }} from the University of Queensland, Australia. They were found growing from rock samples (both full-diameter and sidewall cores) of Jurassic and Triassic sandstones, originally retrieved from an unspecified number of oil exploration wells off Australia's west coast. Depths of retrieval were between {{convert|3400|m|mi|1}} and {{convert|5100|m|mi|1}} below the sea bed. While Uwins et al. present assertions against it, they do not exclude the possibility that the nanobes are from a surface contaminant, not from the rock units cited.

The smallest are just 20 nanometers in diameter. Some researchers believe that these structures are crystal growths, but the staining of these structures with dyes that bind to DNA might indicate that they are living organisms.{{cite web |title=Nanobacteria and nanobes – Are they alive? |website=Carlton.edu |series=Science Education Resource Center |publisher=Carlton College |place=Northfield, MN |url=http://serc.carleton.edu/microbelife/topics/nanobes/index.html}}

They are similar to the structures found in ALH84001, a Mars meteorite found in the Antarctic. A 2022 study concluded that ALH84001 did not contain Martian life; the discovered organic molecules were found to be associated with abiotic processes (ie, "serpentinization and carbonation reactions that occurred during the aqueous alteration of basalt rock by hydrothermal fluids") produced on the very early Mars four billion years ago instead.{{cite news |last=Dunn |first=Marcia |date=13 January 2022 |title=Study nixes Mars life in meteorite found in Antarctica |agency=Associated Press |website=apnews.com |url=https://apnews.com/article/space-exploration-science-business-planets-mars-33dc55ce0ebced0b65322b03ae06feda |access-date=13 January 2022}}{{cite journal |author=Steele, A. |display-authors=et al. |title=Organic synthesis associated with serpentinization and carbonation on early Mars |date=13 January 2022 |journal=Science |volume=375 |issue=6577 |pages=172–177 |doi=10.1126/science.abg7905 |pmid=35025630 |bibcode=2022Sci...375..172S |s2cid=245933224 }}

Nanobes are similar in size to nanobacteria, which are also structures that had been proposed to be extremely small living organisms. However, these two should not be confused: Nanobacteria were thought to be cellular organisms, while nanobes are hypothesized (by some) to be a previously unknown form of life or protocells.{{Citation needed|date=March 2014}}