Origins Center 2017

Some 180 participants enjoyed two days of stimulating presentations and discussions. During a speed-date, they got to know a few total strangers and during the poster sessions, many more participants were able to present their own work.

Session 1: Origin of the Earth and of Life

Snow lines in protoplanetary disks and the delivery of volatiles to terrestrial planet surfaces – Geoff Blake (Caltech, US)

What does it take to craft a planet capable of supporting life as we know it? Geoff Blake, Professor of Cosmochemistry and Planetary Science and Professor of Chemistry (Caltech, US) discussed what we know from astronomy about the origin of Earth-like planets.

Taking the restrictive view of a ‘solar system’ such as our own, several characteristics, like a ‘gatekeeper planet’ such as Jupiter and of course a rocky planet in the habitable zone, are important. Even if less than 0.01 percent of sun-like stars have this configuration, this would add up to 107 such systems in our galaxy. Stars and planetary systems are born in molecular clouds and start with talcum-powder sized dust. The gas in these clouds already contains organic molecules, even including chiral molecules, long before planetary surfaces are assembled.

To study planet formations itself it is necessary to study the tiny regions of dense clouds that are making stars, and with new telescopes it has recently become possible to see roughly which processes take place at different distances from the center of a protoplanetary disk and assess the distribution of water, CO and small organic molecules. Blake: ‘This way, we can learn to understand the processes which occur at different distances in the disk.’

Blake described how Earth has a low carbon and nitrogen content compared to the initial conditions. This begs the question: What is the importance of the amount of carbon/nitrogen for life on the planet? Furthermore, most of the carbon on Earth is located in the deep earth, certainly the mantle and quite possible the core. And as collisions – like the one that probably spawned the Moon – would have blown away any organics on the surface, this could mean that a late exogenous delivery of carbon and nitrogen is important, Blake concluded: ‘You need this late delivery to get carbon and nitrogen in the atmosphere, rather than in the core or mantle, or being blown away.’

Minerals and the origin of life: Insights from big data mineralogy – Bob Hazen (Carnegie, US)

Once you have all the pieces in place – a rocky planet in the habitable zone, the right atoms and molecules – what happens next? You will get chemical reactions, explained Earth scientist Bob Hazen (Carnegie Science, US), and life is based on chemical reactions. Hazen’s work is focused on the role of minerals in the origin of life. He argued that minerals can facilitate such a wide range of reactions that on a planetary (time) scale, unlikely processes become inevitable.

Minerals can act as catalysts, but may also form protective containers or selective scaffolds. In this way, they can create geochemical complexity that is hard to emulate in the lab. The amount of minerals likely to occur on Earthlike planets is huge: some 2,000 have a likelihood of nearly 100 percent, while another 20,000 will probably be present on at least one Earth-like planet somewhere in our galaxy.

‘Each mineral species represents a chemical reaction’, explained Hazen. Given the surface area of clay minerals and average reaction times, Hazen calculated that 1054 chemical reactions could have occurred during the roughly 600 million years before the start of life on Earth. ‘This means that chance versus necessity is a false dichotomy.’ But, someone from the audience asked, doesn’t the origin of life need a chain of different reactions? Hazen agreed, but saw possible solutions: ‘For example, some minerals grow from other minerals.’

Origins of life systems chemistry – John Sutherland (MRC-LMB Cambridge, UK)

Chemist John Sutherland (Medical Research Council Laboratory of Molecular Biology, Cambridge, UK) discussed the chemistry that could have started life from a different angle. Biological life is very complex, so something much simpler must have arisen first, something that could eventually produce subsystems like RNA, metabolism, membranes and proteins. Sutherland started his search for a common pathway that would produce the necessary building blocks for these systems with just a one-carbon feedstock, hydrogen cyanide (HCN). ‘This can be reduced to form carbon-carbon bonds.’ Furthermore, UV-driven reductive chemistry would be a good starting point the create C2 or C3 molecules, which form a product tree that includes a lot of amino acids. Ferrocyanides and other salts could produce further building blocks.

Geochemical scenarios that would produce these reactions include impact shocks that produce HCN from meteoric carbon and atmospheric nitrogen, but also heating and evaporation in a small stream. And H2S produced alongside SO2 from volcanism would act as a reducing agents.

Once building blocks are formed, polymers like RNA could be made. Most of these molecules would be inactive, but recycling of the components coupled to selection would drive RNA evolution, as long as there is an input of energy in the cycle of RNA creation, breakdown and re-assembly.

Towards a bioinformatic theory of the origin of life – Paulien Hogeweg (U Utrecht, NL)

Paulien Hogeweg (Utrecht University, the Netherlands) introduces the final lecture in this session with a question: how did we get from a simple beginning, to life as we know it? In the early 1970s she coined the term bioinformatics together with Ben Hesper, describing the study of informatics processes in biological systems. Using this bioinformatical approach she considers the question on the evolution of life on earth.

Hogeweg showed in models of the RNA world (the hypothesized replicators at the origin of life) how evolutionary dynamics can overcome these obstacles. In spatial models new levels of evolution emerge through self-organization. The presence of parasites (viruses/cheaters) play an important role in this self-organization process and therewith help rather than hinder the evolution of complexity. Hogeweg showed that in a variety of multilevel evolution models division of labor between information storage and information usage evolves. For example DNA as information storage molecule can evolve in the RNA world. This division of labor evolves despite rendering reproduction less efficient. Instead, the unidirectional information flow (‘Cricks dogma’) renders the evolutionary process more efficient and open ended.


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