Ashes to ashes, dust to dust: the cosmic fertiliser that fuelled the origins of life

Ashes to ashes, dust to dust: the cosmic fertiliser that fuelled the origins of life

The questions of how life developed and in what environments geochemical reactions took place are fundamental questions that span the fields of astrobiology, organic chemistry, and geology. One key ingredient is liquid water, which is capable of dissolving and transporting chemicals into and out of cells. Therefore, it is expected that life arose in a watery environment, either within the early oceans, or perhaps in restricted bodies of water.

A study led by Dr Craig Walton (Cambridge University, ETH Zürich) and featuring contributions from Dr Alex Lipp (Merton College, Oxford Earth Sciences), published this week in Nature Astronomy, has challenged the status quo.

The study asks whether natural sedimentary processes, such as those that form beaches and dunes, could have acted to gather cosmic dust particles after they fell to Earth’s surface and thus potentially brought about the origins of life. The continuous rain of cosmic dust provides abundant organic matter from asteroids and comets and delivers it directly to Earth’s surface.

Dr Lipp commented, “It was a real privilege to play a small part in this great study. The results show that high levels of cosmic dust delivery, concentrated by surface processes on Earth, could theoretically produce the ingredients required for the origin of life, billions of years in the past. As a geochemist, a tantalising, albeit very challenging, prospect is whether we can find geochemical evidence of these concentrated cosmic dust deposits in the geological record.”

In Earth’s ancient past, the flow of extra-terrestrial dust was far higher than today. Until now, it has been assumed that since this dust was spread-out across the globe there would have been insufficient concentrations of dust to render it as a fertilising agent. However, by performing a combined astrophysical and geological modelling study, this research has demonstrated that natural sedimentary processes could have played a key role in gathering cosmic dust into more nutrient-rich areas. For example, meltwater pools on the surfaces of ice sheets may have sites where cosmic dust yielded the right ingredients for the origin of life.

“To me this study highlights the importance of working across discipline boundaries. Craig, a cosmochemist, reached out to me for my expertise in surface processes and sediment geochemistry. Working together we identified environments on Earth where cosmic dust might be concentrated in sedimentary deposits, and this led us to glacial environments. Bringing a glaciologist and an astrophysical modeller on board, it was possible to put quantitative constraints on how much cosmic dust might have become concentrated on early Earth in these environments.”

Dr Alex Lipp, Merton College/Oxford Earth Sciences

Today, we can find communities of microbes thriving in proglacial lakes which depend on fertilisation by nutrients, including some small present-day contributions from cosmic dust. Their incredible success in an otherwise inhospitable environment provides a compelling concept. This study asks whether combined processes of cosmic dust accumulating on Earth, nutrients being extracted into glacial meltwater, and stockpiling in closed lakes have fertilised chemical reactions that fostered the origin of life on Earth.

Read the full paper in Nature Astronomy