abstract: Estimates of the time at which life arose on Earth make use of two types
  of evidence. First, astrophysical and geophysical studies provide a timescale for
  the formation of Earth and the Moon, for large impact events on early Earth, and
  for the cooling of the early magma ocean. From this evidence, we can deduce a habitability
  boundary, which is the earliest point at which Earth became habitable. Second, biosignatures
  in geological samples, including microfossils, stromatolites, and chemical isotope
  ratios, provide evidence for when life was actually present. From these observations
  we can deduce a biosignature boundary, which is the earliest point at which there
  is clear evidence that life existed. Studies with molecular phylogenetics and records
  of the changing level of oxygen in the atmosphere give additional information that
  helps to determine the biosignature boundary. Here, we review the data from a wide
  range of disciplines to summarize current information on the timings of these two
  boundaries. The habitability boundary could be as early as 4.5 Ga, the earliest
  possible estimate of the time at which Earth had a stable crust and hydrosphere,
  or as late as 3.9 Ga, the end of the period of heavy meteorite bombardment. The
  lack of consensus on whether there was a late heavy meteorite bombardment that was
  significant enough to prevent life is the largest uncertainty in estimating the
  time of the habitability boundary. The biosignature boundary is more closely constrained.
  Evidence from carbon isotope ratios and stromatolite fossils both point to a time
  close to 3.7 Ga. Life must have emerged in the interval between these two boundaries.
  The time taken for life to appear could, therefore, be within 200 Myr or as long
  as 800 Myr.
authors:
- Pearce, Ben K D
- Tupper, Andrew S
- Pudritz, Ralph E
- Higgs, Paul G
doi: 10.1089/ast.2017.1674
issn: 1531-1074,1557-8070
issue: '3'
journal: Astrobiology
language: en
lastmod: '2018-03-01'
pages: 343-364
path: /library/pearce-2018.html
pmid: '29570409'
published: '2018-03-01'
publisher: Mary Ann Liebert, Inc. 140 Huguenot Street, 3rd Floor New Rochelle, NY
  10801 USA
reference: Pearce 2018
title: Constraining the time interval for the origin of life on Earth
type: article
volume: '18'
year: 2018