How life originated is one of the deepest mysteries of science - this profound question has perplexed humankind for thousands of years. Now, in the twenty-first century, astrobiologists and other scientists have the tools to investigate it; yet, it remains an extremely challenging problem because many variables are unknown.
We had the pleasure of interviewing distinguished astrogeophysicist Dr. Chris McKay from NASA Ames Research Centre about the origins of life and the exciting prospect of discovering life elsewhere in the Solar System.
Dr. Chris McKay in Antarctica. Source: NASA
What was the earth and its atmosphere like when life first emerged? Were there special environmental conditions that enabled or aided the process?
We do not know with any certainty the conditions on the early Earth. In the case of life on Earth, the only fact we have about the origin of life is that it happened more than three billion years ago. We do not know where, when, or how life originated, or how long it took. The hypothesis that the one example of life we see on Earth originated on Earth and/or took a long time is not supported, nor excluded, by any geological evidence. The scientific inquiry into the origin of life is further hampered by the lack of any necessary connection between environments that can support life and environments in which life can originate.
This is a long answer to say basically that regarding the origin of life we are still guessing.
Do you think it's more likely that life emerged rapidly rather than slowly? Why?
The only data we have that is relevant to this is that life is seen in the fossil record on Earth quite early, soon after the surface conditions became habitable. Thus, if we hypothesize that life arose on Earth then it arose quickly.
What do the earliest fossils inform us about the first lifeforms?
The earliest fossils <stromatolites> are microbial mats and the most interesting aspect of them is that they indicate photosynthesis was active.
Stromatolite fossil from Strelley Pool Chert, Western Australia. Credit: Didier Descouens
Hamelin Pool Marine Nature Reserve, Shark Bay World Heritage Site, Western Australia. One of the only places where living stromatolites can be found. Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
What are the key ingredients needed for life?
Liquid water, Carbon, Nitrogen, Phosphorus and some collection of other elements, including salts such as Sodium and Chlorine. Also, Sunlight or redox chemical energy.
Does biological evolution shed any light on the origin of life?
Almost by definition biological evolution is not operative before the origin of life. Life can be usefully defined as a system that does biological evolution.
What are our biggest gaps in understanding how life emerged?
The gaps in understanding how life emerged include: where the life we see on Earth today originated, the conditions that lead to that life, and the time period involved.
What questions do you attempt to answer through your research?
The basic question I am trying to answer is a second genesis. That is a second different example of life not related to life on Earth as we now know it.
What drew you to the second genesis approach and why do you find it to be so potentially fruitful?
The answer to both of these questions is the observation that there is only one life on Earth. It is interesting and probably useful to discover a second genesis.
Do you think life will ever be "generated" in the lab?
So you believe life will be generated in the lab someday! Do you think it will happen soon?
Someday yes, when is hard to predict. I have no insight into the time it might take.
If life evolved on other planets, what would it share in common with life on earth? And how might it differ?
In our Solar System, Mars, Europa, and Enceladus <one of Saturn's moons> are likely candidates. They are carbon/water environments and hence would have carbon/water lifeforms with much in common with life as we know it on Earth (also carbon/water). Titan has carbon but the liquid is not water, it is methane and ethane. Life on Titan, if it is there will have very little in common with life on Earth.
What are the most exciting NASA initiatives in this respect?
1. The search for habitable exoplanets
2. The discovery of the organic and nutrient rich plume of Enceladus and the prospect of a mission to search for life there.
Diagram illustrating how NASA scientists think water interacts with rock at the bottom of the ocean of Enceladus, producing hydrogen gas. Credit: NASA/JPL-Caltech/Southwest Research Institute
See more from NASA about their astrobiology initiatives.