Investigation of a Possible Solution to the Faint Young Sun Paradox: Elemental Sulfur Aerosols

Open Access
Smith, Megan Leigh
Area of Honors:
Bachelor of Science
Document Type:
Thesis Supervisors:
  • James Kasting, Thesis Supervisor
  • Paul Markowski, Honors Advisor
  • Hampton Nelson Shirer, Faculty Reader
  • climate
  • photochemistry
  • aerosols
In 1972, astronomers Carl Sagan and George Mullen presented the faint young Sun paradox, a discrepancy between the predicted subfreezing global surface temperature on the early Earth and geologic evidence of a warm planet. Standard models of solar evolution calculate that the Earth’s surface temperature would have been below freezing until two billion years ago. Geologic evidence indicates that surface liquid water existed long before that time, however. Past research on solutions to this problem has yielded inconclusive results. Atmospheric particles (aerosols) absorb radiation, and may therefore be a possible solution to the problem. Here, two separate investigations of the representation of particles in one-dimensional models are made. First, treatment of particles in a photochemical model is validated, using Saturn’s largest moon, Titan. The results compare well with observations of Titan’s albedo spectrum. Second, an attempt to solve the faint young Sun paradox with elemental sulfur particles is made. The optical properties for these particles are inserted into a one-dimensional photochemical model and a one-dimensional radiative-convective climate model, both configured for the Late Archean/Paleoproterozoic era on Earth (2.2 to 2.8 billion years ago). Inclusion of the sulfur particles lowers the surface temperature by 3 K. Despite the negative outcome, future investigation may yield more encouraging results. Other sulfur allotropes, such as S3 and S4, may increase surface temperatures.