Exobiology and Evolutionary Biology

Aerosols and Clouds on Early Earth

PI: Margaret Tolbert

Photochemistry in the atmosphere of the early Earth may have led to the formation of complex organic molecules, similar to those observed on Saturn’s moon Titan. Previous work in our laboratory has used a novel aerosol mass spectrometer (AMS) to probe aerosols formed in a likely post-biotic early Earth atmosphere. We found a myriad of aerosol organic products were produced with complex functional groups beyond simple hydrocarbons. Thus photochemistry in the early Earth atmosphere might have provided complex organics for the sustenance of early life.

Here we propose to extend our previous studies of post-biotic haze formation to conditions more representative of early Earth before the development of life. Little is known about the composition of the early Earth atmosphere so we will consider a range of possible compositions including CH ₄, N ₂ , H ₂ , SO ₂ , NH~3~ and H ₂ O. A state-of-the-art high resolution AMS will be used for part of this study. One main aspect of this work will be to determine if an early Earth haze could supply life-building organics to the surface of the Earth.

In addition to studies of aerosol chemical composition, we will also examine how early Earth haze particles might directly and indirectly influence the ancient climate. We will use a novel aerosol cavity ring down spectrometer system to probe how early Earth particles take up water and grow to sizes that efficiently scatter incoming solar light. We will also use this technique to evaluate the potential role of early Earth haze particles as nuclei for cloud condensation. As is the case on current Earth, the direct and indirect effect of aerosols on climate could be very large. Thus our measurements will provide key data needed for improving climate models of the early Earth.