ACL: Advent of Complex Life - MIT Astrobiology Team

This MIT Astrobiology Team held a field excusion in early September to Newfoundland to look at the geological and paleontological forces that allowed for the creation of Ediacaran period fossils, which are believed to contain the earliest known evidence of complex multi-cellular life on Earth.  So what does a field excursion look like?  In practical terms, it is a combination of researchers, professors, and graduate students hiking over rocks to study the geology of the region, looking at fossils, takings notes and photographs and asking questions of each other.  Sometimes people think that science is primarily about giving answers, but it is often about asking questions, challenging assumptions, and finding clues that lead to more questions.  This is the way science progresses and the insightfulness of the questioning is a key ingredient of success.

The MIT Astrobiology Team focuses on the environmental, ecological and genetic factors that lead to the evolution of complex life. On Earth, at least 30 different lineages have achieved some level of multicellularity. But organisms with differentiated cells have evolved only six times:

• fungi
• red algae
• brown algae
• twice in the green algae, including all plants
• animals

How such complexity arose is a compelling issue for the NASA Astrobiology Institute for several reasons:

1. Our first indication of life beyond Earth is likely to come from the atmospheric composition of an extra-solar planet (planets not found in our solar system). Interpreting these results will require understanding how atmospheres evolve in response to complex life. This increases the importance of understanding the history of Earth’s atmosphere and how it has evolved in response to life, particularly complex life.
2. By probing temporal and developmental relationships between environmental, genetic and ecological factors associated with the evolution of complex life on Earth, we can productively examine global metabolism (the chemical processes that enable organisms to grow, feed and survive).
3. The spatial and environmental distributions of complex, multicellular organisms are much more restricted than those of microorganisms - they are found in far fewer places. Accordingly, multicellular organisms are more sensitive indicators of the relative importance of environmental, genetic/developmental, and ecological factors in the origin and establishment of evolutionary novelties.

The MIT team's unifying intellectual focus on the requirements for development and evolution of complex multicellularity is motivated by such questions as:

• What combination of genetic, environmental and ecological factors led to the emergence of complex multicellularity on Earth?
• What conditions allow a planet to become habitable by complex organisms?
• What genetic and developmental innovations were required to assemble complex organisms?
• How were the new niches constructed?

Documenting this field excursion was like watching a series of detectives trying to solve a mystery - where the smallest rock or crevice can hold a vital clue that will help us understand the conditions that could have existed 580 million years ago.  Understanding the conditions that would have allowed the organisms that we now see as fossils to evolve and thrive is critical to understand how any complex life evolved, including us humans.  In some ways, the field excursion was like looking back in time at the precurors to modern life as we know it, and asking questions like:

• What did they look like?
• When were they alive?
• What were conditions like when they were alive?
• How are they related to modern species?
• Where did they live?  At the bottom of the ocean?  In shallow waters?  On dry land?
• What did they eat?
• How did they breathe?
• Why were they preserved in this part of the world? 
• What happened to them?

The MIT Astrobiology Team works on answering questions like this, and the field excursion proved a great way to get the team together for discussions, and for some first hand looks at some incredibly preserved fossils from this early life.

August 31, 2009

The team arrived in St John's, Newfoundland for the beginning of the excursion on Monday, August 31.  The entire group stayed in the Battery Inn & Suites, right near Cabot Tower.  

After a group dinner overlooking St. John's harbor, Guy Narbonne, the leader of the excursion, gave us a highlight of what was to come in the next two days, followed by each member of the MIT Astrobiology Team presenting brief talks on their latest work.

We also had a group discussion on how best to utilize and structure the complex-life.org website and the associated EPO activities.  This discussion led to a few important points:

•  Three main audiences were identified:
  • other researchers in the field 
  • teachers
  • the general public
• Because the needs of the three audiences are likely to be very different, the website should offer pathways for each, with different content or activities at the end of each pathway.
• Because much of the content for teachers and the general public (such as photographs, descriptions, and diagrams) will come from primary source materials generated by the researchers, it makes sense to start with tools and materials for other researchers.
• The tools and materials for other researchers will include information about the MIT team, links to publications, lists of references, and an online catalog of Ediacaran biota.  These materials catalog the information created by the MIT team and provide learning resources for teachers and the general public.
• Later on, activities for teachers will be generated using these source materials, in the style of WebQuests.  A WebQuest is a complete lesson plan for a teacher covering a specific topic, including source material, resources, evaluation activities/criteria and related material.

These discussions will help shape the EPO plans of the MIT group in the coming months.

September 1, 2009

This was the first day of the field excursion, focused on the geology of the region and how it has allowed such fine preservation of early life on Earth.  The group traveled in a series of SUVs from St John's to several different points on the Avalon peninsula of Newfoundland to examine the forces that shaped the geology of the region.  In particular, the group, led by Guy Narbonne, was interested in the various sedimentation and glacial events that would help indicate the point in Earth's history where oxidation of the ocean may have occurred.  This is important because complex multi-cellular life (such as animals) are dependent on this oxidation, and so you would only expect to find fossils in the rocks above that point (later in time).

In the photo above, we see Guy showing the location of a "cap carbonate", which is indicative of a potential "snowball Earth" event.  A "snowball Earth" event refers to a climate state where glaciers potentially reached the equator and possibly covered much of the ocean. Such a condition would explain geological glacial formations found in rock layers that would have been close to the equator when they were deposited.  Since the continents are constantly drifting, some of those rocks are now very far from the equator, although geologists can tell where rocks were on the Earth when they were deposited by looking at how the magnetic fields are lined up. (For the latest information about Snowball Earth science see Paul F. Hoffman’s outstanding website: http://www.snowballearth.org/)

Cap carbonates come from carbon dioxide that gets disolved in the ocean and is "precipitated" out once the concentrations exceed the saturation point.  The process for producting cap carbonates goes something like this:

• "snowball Earth" causes the planet to be (nearly) covered in ice - it's COLD
• volcanic eruptions continue to send out carbon dioxide, but now this carbon dioxide is trapped in the atmosphere and cannot be absorbed by the ocean (which is covered in ice)
• at this point, the atmosphere builds up with carbon dioxide, and you get...well, you get a sudden global warming, just like we are have now with carbon dioxide emitted by cars
• this "greenhouse effect" starts to increase the temperature of the Earth, causing the ice to slowly melt
• at the same time, the excess carbon dioxide in the atmosphere dissolves in rain and accerates weathering (dissolution) of continental carbonate and silicate rocks.
• when these weathering products (incuding excess calcium) are delivered to the ocean through rivers, calcium carbonate re-precipitates and forms a cap carbonate

The particular cap carbonate shown above is found at the top of the "Gaskiers" formation, which was timestamped at ~580 million years ago, meaning that a global glaciation event likely occurred immediately before the Ediacaran period (the period where the first fossils representing complex life are found).

In the photo above, we see clear iron oxide banding lines in rocks close to the Gaskiers formation, indicative of the various sedimentation layers that were layed down during this time.  This offers evidence that oxygen was found in the atmospere and the ocean during this time period, spuring the development of complex life.  What we are seeing here is basically rust - which takes oxygen to form.  It is estimated that at the times these rocks were formed 580 million years ago, the atmosphere contained about 10% oxygen (today it is ~21%).

And, yes, in this part of Canada, you actually do need an SUV to get where you are going.

And bring your hiking boots because those rocks and fossils are sometimes found in out of the way places.

This is a "mother-in-law door", a common feature of houses in this part of Newfoundland.  It is the front door, that goes nowhere and is apparently designed to be used by two people: tax collectors and mothers-in-law.

September 2, 2009

The second day was focused on looking at and identifying Ediacaran fossils.  We traveled to different sites, with the last and most important one being the Mistaken Point assemblage. The trek included a river crossing, and hikes down some steep embankments to reach the fossils.

Fossils are only deposited in exactly the right conditions:

• First, you need a form of life that can turn into a fossil.
• Next, you need the right surface for the organism to be 'pressed into' (which acts like film in a camera).
• You also need a material to compress down enough to form the impression.
• Finally, you need a lot of time for the fossil to form.

Where all of these conditions are present, such as places like Newfoundland, we find fossilized complex life.  However, there are still large gaps in the geologic record where no fossils are found, since all of the right conditions did not exist.  It is likely that organisms existed, but the geological conditions were not right to form fossils.  This leaves us with only small snapshots of time, sometimes separated by millions of years, in which to watch evolution occurring.  By understanding the evolution of life on Earth, we can better predict how it might be occuring on other planets, such as Mars.  For example, John Grotzinger, of the Astrobiology Team from Caltech, uses his knowledge of geology and sedimentology on Earth to help NASA decide where the upcoming Mars Science Lab should search for life.

One of the challenges involved in studying the fossils includes trying to understand their taxonomy, or how many species are represented in the fossils and how they are related to each other.  By looking carefully at the structures preserved, members of the team are working to create an early 'tree of life' to place these extinct species into groups and understand not only their relationship to each other, but also how they are related (or not) to modern species of animals.  This is challenging, since without a time machine, as one team member put it, all we have left are all of the clues in the rocks.

In the photo above, we see Roger Summons (MIT) using the GigaPan camera lent to us by NASA to take a wide-angle shot of one of the Mistaken Point beds. The Mistaken Point assemblage of fossils is incredible, with several large "beds" of rock containing many many hundreds of fossils - so many that it's impossible to stop yourself from walking on them. Note that in order to wander around the Mistaken Point rock beds, we needed to wear special footwear so as not to damage the fossils (you can see the soft blue footwear on the person in the left of the picture).

The photo above shows one of the Mistaken Point beds where many of the Ediacaran fossils were found.

The image above shows a fossil of a circular "holdfast", or the point where the organism was anchored to the bottom of the sea floor (to the left of the coin).  Note the typical geologist technique of including an easily identifiable object from their pocket in the picture so you have a sense of scale.  In this case, it helps remind us which country we were in too.

The image above shows multiple fossils, some complete with their holdfasts, and branching structures.

Photo by Phoebe Cohen

The image shows the incredible detail that has been preserved in some of the Mistaken Point fossils.  Very fine structures are visible in this photo, sometimes to a scale as small as millimeters.

The Photosynth image above allows you to zoom in and look in detail at a Bradgatia linfordensis, a fossil at Mistaken Point.  You will need the free Silverlight player to view the synths.

The Photosynth image above shows a 360 degree view near Mistaken Point, Newfoundland.

A Flickr group for the MIT team is also available, containing even more pictures from the Field Excursion!

Photo by Dan Segre

The photo above shows the MIT team, with the coast of Newfoundland in the background, enjoying another sun filled day of fossil hunting.

We are grateful to Guy Narbonne (Queens University, Kingston, Ontario) and Marc LaFlamme (Yale University) for leading our excursion. We are also indebted to Manager Richard Thomas and staff of the Mistaken Point Ecological Reserve for coordinating our visit and providing logistical assistance. Our research on the Advent and Maintenance of Complex Life is funded by the NASA Astrobiology Institute.