[music playing]
- Welcome to the 2016 NASA Ames Summer Series.
Life can be considered as an expanding, complex,
dependent set of chemical reactions
that, once began, has optimized its capabilities
to occupy various environments.
Today's talk is entitled:
"Subsurface Astrobiology:
Cave Habitats on Earth, Mars, and Beyond,"
and will be given by Dr. Penny Boston.
Dr. Boston is, as of May 2016,
the Director of the NASA Astrobiology Institute.
Prior to that, she served as an associate director
of the National Cave and Karst Research Institute,
and professor and chair of Earth and Environmental Sciences
Department at New Mexico Institute
of Mining and Technology.
She received a Bachelor's of Science
in microbiology, geology, and psychology.
Wow.
Then a Master's of Science
in microbiology and atmospheric chemistry.
For the interns, look at diversity.
And followed with a PhD,
all from the University of Colorado Boulder.
She has numerous publications and awards--
too many for me to mention here.
Please join me in welcoming Dr. Penny Boston.
[applause]
- So, it's lovely to have the opportunity
to talk to you about some of my favorite things
and some of my favorite things are caves.
I started working in caves about 25 years ago,
after already being in mid-career
and working in other extreme environments.
And I was not a caver recreationally.
A lot of folks who find their way in cave science
do it because they are sport cavers
and explorers and stuff,
and they really want to run with that theme
and figure out how to make a living out of it.
You know, I'd been in the usual number of caves as a kid,
show caves, and I thought they were really cool,
but I had not connected those to my science.
And it wasn't until in the early 1990s,
I wrote a paper with several colleagues--
one of whom is here, Chris McKay--
suggesting that the last best place to look for life
that was still alive on Mars would not be on the surface
where the conditions were really, really tough,
but actually in the subsurface.
And so that got us thinking about
how we could get into the subsurface
and, you know, we were still young
and not all that well-endowed with funding research.
And so the idea of drilling was compelling,
but it was really expensive.
And we couldn't get any of the old, established guys
to let us get our foot in the door.
And so we saw a "National Geographic" special
about this really amazing cave
in New Mexico called Lechuguilla.
And this is the deepest cave in North America.
It is an enormous system.
It has currently
about 140-something miles of mapped passages.
It's a gigantic maze system.
And in this "National Geographic" special,
they said a couple of really important things.
One is that it was a pristine system that had to be dug into.
So that meant to us that, perhaps,
there would be minimal human contamination in the system.
The second thing was
that it had all this exotic sulfur mineralogy.
And for those of you who know anything about Mars,
Mars is a pretty sulfur-rich planet.
We've known that ever since the "Viking" missions.
And then the third thing was that there was a USGS scientist
named Kim Cunningham, who was on camera
and said that he thought he had seen
what he thought were microorganisms
in his scanning electron micrographs
of some of the cave decorations in there.
So I called him up and I said, "Hi, Dr. Cunningham.
You don't know us, but we're from NASA
and we'd like to go into your cave."
And he said, "Okay, so cool!"
He was a boundless enthusiasm kind of guy.
And a lifelong caver,
which was an asset but also a detriment,
because he didn't understand how very hard that would be
for those of us who were not cavers.
And so we trained for all of three hours in vertical work
in Boulder, Colorado, where I was then living.
And we went down to Lechuguilla Cave
and went in for a five-day expedition.
And it nearly killed us.
And the whole time I was in there, I just kept thinking,
"All I have to do is live long enough
to get out of this bloody place
and then I never have to come back."
And so that was the inauspicious beginning to my caving career.
But what I discovered when I got out of the cave
was all the bruises,
and the eye that had swelled shut from stuff getting in it,
and the busted ankle, and all that stuff,
started to heal.
And then what we do as humans is kind of remodel the past, right?
This is why we have more than one child, usually.
[laughter]
And so I began to forget about the bruises,
and the pain, and the stress,
and how I wasn't even slightly up to the task
of being in this environment.
And what I remembered was what I had seen.
And what I had seen was the most exciting set
of environments that I'd ever seen in my life.
And each room was different.
And this was an amazing environment,
unlike anything that I had ever seen before.
And that's really what got me started.
And I refocused a great deal of my work in that direction,
so that's really the answer to this, you know?
Why would you go into these places
that are working hard to try to kill you?
'Cause, you know, it seems glamorous,
but really it's a whole lot of no fun.
I mean, it's really a lot of work,
a lot of stress to try to keep ourselves safe.
So I always look goofy, because we're in environments
where we have to actually protect ourselves, right?
So all of the glamour shots that you see here
are me in one kind of protective garment or another,
or just liberally covered with mud,
because that's the other part of it.
You have to really like getting dirty
in order to operate in these environments.
So that's the fun part, is playing with mud pies.
But the serious part is that
it's very difficult to do microbiology
in such a dirty environment,
and so we've had to really learn how to, you know,
alter our techniques to actually cope with that.
Well, so that's been a lot of my gig
for the last quarter century and of course I've taught
and done research in different institutions and so forth.
The new gig is really pretty different in a way,
but it's informed by my feel for what it's like
to get out into natural environments
and interrogate them.
And so I have great respect for the astrobiology community,
which is an enormously diverse community.
So the new gig is basically this.
We are housed here at Ames,
and we are a virtual institute
to do with all of these kinds of questions that you see up here.
We're part of the overall NASA astrobiology program,
which is managed and run, and directed from headquarters.
Like all NASA things, right?
You can't get away from org charts,
so this sort of shows how the Science Mission Directorate
is kind of the overall lovely and happy
unicorns-and-sparkles-rainbow over everything,
and then the Planetary Sciences Division is nested within that,
and astrobiology, in turn, is nested within that.
And all of those little green fruits hanging off
are parts of the astrobiology program
that are run out of headquarters.
And then, of course, NAI
because we are the sparkly galactic center of the universe.
We are here.
It's been fun to get used to being queen of NAI,
and it's quite an enterprise.
There's over 600 different individuals
currently involved in the program.
This is a mix of senior science folks, postdoc students,
and a whole bunch of different lead institutions.
[coughs] Excuse me.
The lead institutions only are the primary places
where the different teams are run out of,
but of course it involves a lot of other different institutions.
And so this is a very exciting
intellectual environment to operate in.
So when I think about astrobiology,
there are, you know, fundamental questions that we have.
[coughs] Excuse me.
There are fundamental questions that we have.
And one of the ones that was quite apparent to people
very early on in the Space Ages,
illustrated in this really classic cartoon
from "The New Yorker," which appeared in 1962.
Already, the press kind of understood pretty well
what part of our job is.
And that is to think about
life-forms from first principles.
What is life?
What does that mean?
What are the implications for that--for actually looking
for organisms on other planets
when you have no idea what they're gonna be like.
And so in a remarkable turnaround,
this has been one of the most instructive things
that we could've done for understanding life on Earth,
because it caused us to really think
in a much more fundamental way about how life operated here.
And it stimulated people to go to the ends of the Earth,
both physically, chemically, thermally,
to try to see what life here could actually do.
So astrobiology in general,
within the framework of NASA's conception of it,
really has three major arenas that it is focusing on.
These three fundamental questions.
What is the very origin of life,
and how does it then evolve in a planetary context?
Planets give rise to life, they have here in our case,
and we work under the uber assumption
that this is true broadly throughout the galaxy,
and undoubtedly, beyond.
Does life exist elsewhere in the universe?
And how do we go about looking for it,
and how do we recognize it when we find it?
And in fact, there really fairly philosophical implications
of this, which involve what the future of life
on Earth is and beyond.
So if you really look at astrobiology,
it's not a fundamental core science.
It is a place-based and problem-based science.
And it really involves all of these sciences,
particularly a really large dose of engineering,
because we need missions to actually go to places
where we want to look for life.
We need instrumentation that can allow us
to detect things that are not obvious.
If the life were big and were gonna bite us on the ankle
like it does in a lot of science fiction movies,
it wouldn't be such a hard problem.
But we think primarily that we are looking for microorganisms,
which we have a hard enough time studying here.
The biology and the environmental aspects
of extreme environments are-- of course,
encompass a lot of my work
and that of many other people in the community.
And then of course, all of this is highly informed
by the entire spectacular sweep of astronomy.
Everything from the creation in stellar nucleosynthesis
of the elements that go to make up our kind of life
and perhaps other kind of life,
all the way to how do we get the formation of solar systems?
How do we get planets?
What does that mean?
What kind of planets do we get?
What are their endowments of riches that they can bring?
As some of them undoubtedly develop
into life-bearing planets.
Well, there is a fundamental similarity
between astrobiology in that regard,
and the study of caves, which is called speleology.
In that it is also a collaboration
of all these different sciences.
And my area has mostly focused around
what we call geomicrobiology,
which is the interaction of microbial forms
with the rock and mineral environment in which they live.
So what is the real estate?
This is kind of it.
This is a beautiful picture
of one of the most spectacular caves in the world
that, luckily enough, was about an hour and a half drive
to the entrance of the cave from my former university.
And we were the science leads on the exploration of this cave.
This is a cave that had been known for a very long time,
and actually trashed out and then rehabilitated
by a local caving grotto.
The avocational caving community provides
thousands and thousands of hours every year
of free labor to federally-managed lands
and is a major part of conserving these environments.
And so the beautiful whites river
that the young lady is standing on is known as Snowy River,
and this is the single largest, by orders of magnitude,
single largest cave decoration in the world.
By "cave decoration," we mean things like stalactites,
stalagmites, but a lot more exotic stuff.
And this goes on for 18.5 kilometers so far.
And we are still exploring it.
So anything in a rock fracture is really part
of the same kind of subsurface microbial habitat.
All rocks fracture at some level
and those fractures are living space for microbes.
Those special parts of that rock fracture habitat
that store water--
very important to us as a species, known as aquifers--
those are even richer.
Because they have the potential
for transporting materials more freely.
Caves and mines are significant
because these are windows into this rock fracture habitat,
and they're also even richer in niches.
Because you have the interaction
of both the gas phase, the water,
and the solid rock material.
And so you have just this amazing array
of habitats for organisms to inhabit.
This is not just true on the terrestrial landmasses.
Those are the areas that I work in.
I primarily work in air-filled caves,
although I've done some work in water-filled caves.
But the ocean floor itself is highly fractured
and completely infested with microorganisms,
down to at least a number of kilometers,
maybe five, maybe ten.
We don't really know yet.
So the message here is that the entire crust of Earth,
down to five or ten kilometers,
is heavily colonized by indigenous--
that means organisms that have always been there--
life-forms.
And this is a hidden part of our biosphere
that, really, we only began to have an emerging picture of
over the last 20 years or so.
So that beautiful, sparkling, white structure
I show it in this image here--
you can see it on the right-hand side--
and that's beautiful.
But what we were really interested in
is all that dark stuff you saw in the previous picture.
All that dark material that you may or may not have noticed
on the rocks, that's where the microbial action is.
That is completely deposited and created by the organisms
that are busy eating the bedrock of that cave.
They're not just hanging out there.
They're munching down a lot of that material,
and this makes them a very unique life-form.
They're geologically active
and they're doing all kinds of things to transform the planet.
So one of the most fascinating things about the subsurface
is just how different it is.
This is one of my favorite examples.
This comes not from my work, but from colleagues,
John and Susie Pint.
Susie's Mexican, John is a British fellow,
and they do most of their work in Saudi Arabia or Oman.
You can see the background picture, of course,
is the Rub' al Khali,
which is a very dry, sand dune desert.
Very famous area, the Empty Quarter.
And within that area geographically,
there are many caves.
And you can see Susie peering down on the left-hand side.
She's peering down into a small opening.
You can see the lower center picture
shows someone repelling,
is rigged on the surface and repelling down
into a really big one.
And when you get in there,
you have literally gone to a different planet.
You have gone to an area where there are diveable pools,
where the biology that is inhabiting those pools
are relics from perhaps 20 million years ago
when this area began to become a desert.
So these are time capsules and it's such a different world
even in the cases where you have these big, giant gaping holes.
You still have enough of a boundary condition
to make the subsurface wildly different from the surface.
There's some really obvious stuff about the subsurface.
One is you don't have sunlight past that entry zone.
So this means you don't have photosynthesis
playing a big role in the food webs of caves,
at least not directly.
So there is transport of organic material and nutrients
from the surface-- from the surface biomass.
But you have that stress on the environment,
but you also have very benign conditions.
So the fact that caves tend to be high humidity
and very constant in temperature within a given cave--
even though different caves have different temperatures--
this is a very benign aspect of the environment.
So organisms benefit from that.
They pay the price when it comes to making a living
and what they have for lunch.
So those are the challenges for them.
There are typically very low organic nutrients
in these environments, but they're mineral-rich.
So the kinds of organisms that I have studied--
and I'm very interested in--
are ones that make their living not off organic material
like we have for lunch,
but off redox transformations or oxidation transformations
of metals and other minerals in the environment.
And they get tiny amounts of energy
from that small numbers of quanta of energy,
and they couple that to carbon fixation,
just like plants do with photon energy.
So it's a similar process.
They're making food.
They're making more of themselves,
but they do this without benefit of sunlight.
One of the great things about caves
is that what happens in the cave stays in the cave,
in many cases.
So you don't have ordinary surface weather.
And this means that a lot of these microbial processes
and, in fact, even macroscopic organisms
will self-fossilize in these highly mineralized environments.
And so you can see the traces of even past life,
without the usual processes of life being buried
and then replaced and fossilized
in the way that we normally understand it.
So the geomicrobiology itself is a very elaborate
and complicated area of science.
But really, it boils down to this:
what do microbes do
when they interact with rocks and minerals?
And the things that grab my attention the most
is that they are master chemists and transformers of materials.
So they destroy bedrock at a significant rate,
and then they take that stuff that they munch
from the bedrock or disaggregate from the bedrock,
and they basically poop out unique biominerals.
And you can detect those biominerals,
and those biominerals are clearly,
in many cases, a product of life.
The textures and even the patterns of the precipitation
of those minerals are an indication of life,
or what we call a biosignature.
So a biosignature can be anything as obvious
as a big giant dinosaur bone,
or it could be as subtle as isotopic shifts
in the geochemistry of the environment.
So there's a long list of cool stuff that geomicrobes do.
This is just a list here.
They really are geological weathering agents.
They probably are involved in a lot
of low-temperature economic minerals that we mine,
so they have a lot of practical value.
And they produce all these wonderful minerals.
And I'm a mineral collector.
I don't know if there's others of you in the audience who are.
But a lot of those exotic minerals seem to be
the product of microbial activity.
They produce things that we can use
that are completely underexploited at this point,
so they are in an extreme competitive situation.
And they are competing with each other
for the limited amount of energy
that's available in the environment.
And this seems to cause them to make
a very large array of different kinds of chemical compounds
that they can use to keep each other at bay, okay?
So it's almost like chemical warfare, in some sense.
And these have potential pharmaceutical potentials.
There are many, many different antibiotics
that they are producing that are completely unexploited.
Certainly low-temperature enzymes
that can be used for industrial processes.
On the more esoteric and strictly scientific side of it,
we almost never find anything that is known to science.
When we do the genetic analysis of these guys,
almost everybody is novel.
They are no more than maybe 90% congruent
with other known life-forms in the database.
This is an unknown world.
And there are implications for the very origins of life
and its early evolution.
Some people have actually suggested that the subsurface
might be a more benign place to actually generate
the prebiotic chemistry that you might need.
Who knows?
That's a very difficult thing to even study or think about.
Well, when you wrap all this fabulous package up, of course,
one of my main focuses has always been--
and now is pretty exclusively--
the astrobiology implications of a subsurface biosphere
of such biological richness.
How do we translate that into something
that we can understand?
This is one of the big challenges of astrobiology.
We are really being asked to write a field guide
to organisms that we don't even know exist.
And that harks back to that cartoon
that I showed you from "The New Yorker,"
which is we have to think through a lot of this stuff
from absolutely first principles,
informed by what we can learn from the environments here
and what our kind of life can actually do.
How can our life push up against
the envelope of these difficult conditions?
So let me turn for a minute to the issue of caves.
So I've mentioned caves
and talked about the fact that I work in them.
Why?
Originally, it was because the environment was so entrancing
and so chemically different in many cases--
or different in terms of temperature
or other features that were extreme--
and that's what really drew us.
But, you know, I have a background
in planetary science too, and so it was immediately obvious to me
that we should be thinking about where and how
we would look for caves on other planets.
This was at a time where no such thing
had been actually really detected.
So at first, it was an exercise in complete speculation.
But we thought about this deeply
and how we would approach it.
And what became clear was there was a sliding scale
of what you could actually see.
And in the early 2000s, we began to realize
as we sent missions back to Mars
and we had this orbital platform,
this imaging capability once again,
that we were seeing things that looked very much like
volcanic caves, a byproduct of different volcanic processes.
And now we know that there are tons of them on Mars
and the moon, and in fact, other bodies as well.
But there are first principles arguments here.
So if you go down my little slider there,
in the direction of speculation,
you have lots of ways of making cracks on a planet,
both internal and external forces.
Internal seismic events that may occur on some bodies,
maybe not on others.
But every body in the solar system
is being hammered by external impacts.
And those external impacts create cracks,
and when you have cracks, you essentially have caves.
If you have fluid in the system of some sort,
you have the potential for enlarging those,
but you don't even need that.
So there's lots of ways to produce holes
in the crusts of planets.
And if you really let your imagination reign,
you can think about mechanisms
that are maybe not represented here
in the cave types that we have on Earth.
Well, some of this is not really new.
I mean, some of this we've known about for a long time,
really from the early part of the Space Age.
Ron Greeley, who unfortunately passed away a few years ago
as a very eminent, elderly scientist at the time.
And early on in his career,
he grew up in the Pacific Northwest
amongst lava tubes and volcanic features.
And understood immediately that on the moon,
we were seeing features that were remarkably,
geomorphically similar
to the kinds of things that he had grown up on.
Well, now our eyes have been opened
and I just put together a quick potpourri
of different bodies where you can see features
that appear to be lava tubes.
You can see here-- the moon and Mars and even Io.
And even Mercury-- who knew that?
And new processing of the old Venus data--radar data--
that now allows us to interpret better
than we did at the time the data was collected.
All of these bodies have clear indication
of volcanic cavities of one kind or another.
It's interesting that even though Ron Greeley
and others were pointing to the similarities
between the volcanic terrains that we have here on earth,
in the early days of lunar exploration,
it was 40 years before actual caves
were confirmed on the moon.
That was in 2009 and this was because of the lack of missions.
This was not because of the lack of thinking power.
So I just want to show you one of these monsters.
This is from the fabulous HiRISE camera
that has been opening Mars to our inspection
in a way that nothing else has.
This is a really big feature.
It's 100 meters across.
And if you are not familiar with thinking about
what 100 meters is, that's what it is.
We are always looking for analogs here on Earth
that we can tap into to get a feel for this.
And so on Google Earth, wandering around one day,
I found this sinkhole in Utah.
So as we were doing--you know, we've been doing research
in Utah for many years and other environments,
and so we drove out to it.
Pickup for scale.
This is about a quarter of a diameter
of that Martian feature that I showed you,
to give you a feel for what this looks like.
Doing work in the Galapagos Islands a couple of years ago,
this is about an 80-meter-- so, approaching the size--
and as you can see on the far rim,
there's little tiny people over there, to give you a feel.
And of course, this is not Mars.
It's tropical Earth.
So there's green scum all over everything.
But you can imagine this on Mars,
without all of that vegetation.
So the message, really, on Earth
is that we have caves and just about every rock type.
If you go to a lot of tourist caves,
you come away with the idea
that everything is made out of limestone.
This is not the case.
We have a lot of limestone on Earth,
and we have a lot of water on Earth,
and so we have a lot of limestone caves.
But you can make caves with a variety of geological processes,
and all of these materials and more.
So that got me thinking about first principles.
This is the wordiest slide and all you have to do
is look at the pretty pictures on the left side--
the pretty colors, rather, on the left side.
Try to get divorced from our earthly thinking
about these kinds of features.
I first published, in 2004, a scheme
for looking at the fundamental physics and chemistry
of the different kinds of ways to make caves would be.
And this is a work in progress.
We revisited it in 2012.
We're revisiting it again now.
And now what we're trying to do
is actually look at what we know about
the bodies in the solar system.
And you can see I have added another column on the right,
where we're trying to say that these kinds of processes
are possible on those bodies
and give us a menu for what to look at.
I want to turn now quickly to the Icy Satellites.
From my cave perspective, these are not ocean worlds.
They're planet-sized aqueous caves.
They are roofed structures, they've got ice over them.
And if you actually look at
what you want to maybe look for there,
there are a whole lot of features.
Not only the planet itself,
but also features that may occur
for which we actually have analogs here on Earth.
I'm not gonna go into detail here
because I don't want to run totally out of time
before I show you some more cute cave pictures.
We have features like that here, these are--
three of these images,
the two on the left and the upper right one,
are in association with the active volcano in Antarctica.
These are fumarolic towers on the surface
with caves underneath them.
So this is a potential model for these icy worlds.
The lower right is from Mount Rainier.
There are fumarolic ice caves there.
In fact, my team is in the field right now.
My colleagues on this expedition,
back to our sites there.
This is a new "National Geographic" supported
expedition of ours.
So I want to show you just a couple of pictures
of some of our greatest hits.
That upper right-hand side is another image
from that Mount Rainier site.
This is significant in terms of astrobiological environments
because it is very cold.
It's about -3 degrees C.
It has all sorts of gases that we find poisonous,
but that the microbes living in there
are actually using as energy sources.
On the other end of the heat spectrum is the lower left.
This is 40 to 60 degrees centigrade.
Something like, you know, 140 degrees Fahrenheit.
And this is a very hot system
where we also see that microbes rule the day.
All that orange stuff you see on the walls,
all of those beautiful, gigantic crystals contain pockets
with trapped microorganisms in them
that are still alive after tens of thousands of years.
The upper left image shows one of our caves
that we've been studying since 1998.
This drips with sulfuric acid
and we have to go in all these protective suits
and breathing gear and all of that.
But it's one of the biologically richest caves in the world.
And this is because stuff that we find poisonous
is actually the base of the food chain.
That hydrogen sulfide is feeding bacteria.
Bacteria are feeding everybody else.
Everybody's happy.
There's bats in there.
Who knew that bats could tolerate this?
They're much tougher than we are.
So this has made me think
that there are really two different kinds, at least,
of biospheres possible.
The one on the left is our kind.
It's obvious, it's conspicuous.
There's life all over the surface.
You can pick up that signal
of the chlorophyll spectroscopically.
Maybe even from another stellar system.
We are in an obvious type of biosphere.
But Mars or Europa and the other icy moons
may be very cryptic and may be very, very difficult
to get our teeth into.
Some of the things that we're looking at
are macroscopic indications of microscopic organisms.
So even though the microorganisms themselves
are individually minuscule,
when you put them all together,
and they have this wonderful ability
to transform their environment, they produce spectacular stuff.
They produce red towers packed with tulip-shaped microbes
that coat themselves in iron.
They transform copper from sulfides
to sulfates and oxides and silicates
and produce all of that blue stuff
that you see dripping down
in that particular cave in Sardinia, in Italy.
They produce obvious goo.
So the "snotites" in the upper center
are the favorite thing that I talk about with second graders.
And I like them a lot too.
Some of our stuffy colleagues once suggested
that we not call them "snotites,"
that we call them "microbial veils."
And I'm like, "You got to call a spade a spade,
and you got to call snot, snot."
Because it gives the right idea and chemically,
it's much more similar to snot.
So all of these examples are there for us to see.
The biodiversity is fantastic.
I will not bore you with actual data.
I will just show you a pretty picture.
But I will tell you that we have hundreds of thousands
of strains of organisms that are no more than 90% related
to any other strain on Earth.
This biodiversity far outstrips
probably the entire biodiversity of the surface put together.
And we've only just begun to scratch the subsurface,
so to speak.
You know, you're looking at a large percentage
of the world's community that do this kind of work,
standing here before you.
There's not more than 20 of us distributed
throughout the world.
We're trying to change that, but...
So any of you students who want to work in this,
there's a lot of low-hanging fruit.
Energy-enriched environments--
this is that sulfuric acid cave that I showed you.
All of those organisms are living in there.
The "Snotites" are the most famous ones.
But the stuff that I'm holding in my gloved hands,
we call those "Phlegm ball mats."
You may be picking up a theme here--
when you're in a cave like this that's just dripping with life,
the analogies to the human body or any body is really in there.
Those live in anaerobic conditions.
There are worms living in there,
in the complete absence of oxygen,
so that's a highly evolved metazoan animal
living in essentially zero oxygen.
The fish are highly adapted
to this environment that poisons us.
These are also vertebrates.
Five species of bats, including vampires,
regularly live in here,
and, in fact, have babies in here.
And how they do that under those circumstances, I don't know.
So there are probably 30 or 40 PhD dissertations
in that cave alone.
We produced three.
So there's much to be done.
This system has gained a huge amount of attention
and that is because of these giant crystals.
It's been the subject of two "National Geographic"
television specials, several different articles
in "National Geographic,"
media people from all over the world have covered incessantly.
We were privileged to go head up
two of those "National Geographic" expeditions.
This was a rare opportunity
because this system was only available to us
because they were dewatering the entire system for mining.
So these were caves--are caves-- that have no natural opening.
And we only were able to access them
because the miners accidentally broke into them.
They are in a very hot environment.
So you see us in the little orange suits.
You might think we're trying to stay warm.
We're actually packed in ice
in order to endure this environment.
Even packed in ice,
we can only stand it for about 30 minutes,
and then the stress on the body starts to cook your brain
and your limbs become weak
and it really becomes life-threatening.
And I learned that when I stayed in for 55 minutes
because I was really trying to get this sample.
And really, it nearly killed me.
So I kind of learned my lesson.
Although, once again,
I never retain that information for too long.
So this is kind of the general scope.
There are these giant ceylonite crystals.
This is the same mineral as wallboard,
intrinsically, chemically-- it's not that exotic.
But the form in which it finds itself is spectacular.
And it's very hot.
The water that was drained for mining
has now reinvaded the cave.
So this is no longer accessible as of about six months ago.
The mining company, Peñoles,
which is one of the big Mexican mining companies--
this is a commodity mine with zinc and copper and lead--
the commodity prices were no longer supporting
the $7 million a year in pumping costs.
So this is now flooded.
This was a precious little snippet in time
where we could actually study this system.
But we have lots of samples.
We have genetic analyses of a lot of the organisms in there.
It's the saturated humidity.
And as interesting as the crystals themselves
are all that orange stuff on the walls.
That stuff is alive.
And so what first persuaded me to go into this system
was the images that you see on the left.
Electron micrographs sent to me by an Italian colleague,
Paolo Forni,
who's one of the great cave mineralogists of the world.
And he said, "You know, I think these are microbial fossils.
What do you think?" And I'm like, "Oh, yes.
They so are.
We've seen this kind of stuff elsewhere."
So I was sold and I was expecting
to find a lot of fossil material.
What we found instead is that those orange walls
are entirely encrusted with what you see on the right.
Those filamentous little guys
are diving in and out the iron oxides.
They are very weird organisms.
Their closest relatives are organisms
from the Kamchatka Peninsula,
a cave in Italy, and a cave in Australia.
You explain that to me.
I have a theory.
So, the results so far
is we've done age dating with other colleagues.
The big crystals themselves are about half a million years old.
There are pockets within those.
And within those pockets, we were able to--
because we know the growth rate of the crystals now,
we were able to determine how far in time we were reaching
as we sampled within the crystal structure to get some of these.
And that ranges from 10,000 to 50,000 years
that the organisms trapped in these have been alive.
That was the biggest surprise.
We were actually really trying to just look for DNA
that we could extract to see if it had still survived.
And what we found was actually live guys.
So this is, you know, very exciting.
We've not yet published this
because I am very cautious about these things.
And we're doing a lot of additional work.
There is a huge virus load in there.
When you have a huge virus load,
that says indigenous environment and indigenous community.
Let me tell you one more case study,
and then I'll wrap up.
So the hunt for blue goo is an interesting story.
It did not start in a cave or a mine.
It actually started in the mineral cabinets of Harvard.
So Carl Francis was the curator of the Mineral Museum at Harvard
at the time, and we were on a completely unrelated field trip
to go look at pegmatites 'cause I'm a mineral collector,
you know.
And he was whining to me at dinner one evening
about his copper sulfides.
I mean, you know.
That's what you talk about and such things.
And he was saying, "God, you know,
we pull all these out of the cabinets
and we go at them with the toothbrushes
and they're all beautiful and we put them back in the cabinets
and in about two years they're all brown and ooky again."
And he said, "Do you think that that could be
some kind of life, you know?
Could it be some kind of contamination?"
And I said, "I have no idea.
But, you know, give me the pieces and we'll go look."
And we looked and sure enough,
it was covered with all these bushes and all these organisms,
and so that got us really started.
And then once we started to work on that,
we discovered that in a lot of the caves
that we had already been studying in Hawaii and Venezuela
and Mexico and other places,
that this stuff was actually going on
in the natural subsurface.
So this wasn't just Harvard.
It actually was a global phenomenon.
So we've been studying these for a long time, since 2001.
They grow really slowly.
And even though we do genetic analysis on stuff,
from my point of view, as someone who wants to see
what kind of minerals, what kind of bedrock these guys eat
and what kind of minerals they poop out,
I really need to grow them.
So a lot of my work is a zoo-keeping function.
So it took 30 months before we saw anything.
I was sort of about to give up.
And then about four and a half years into the process,
we began to see that they were indeed transforming materials.
Now they're 15 1/2 years old.
Same plates, okay?
That's a whole other story about how you keep microbes
living in plates that long.
You can see some of the electron images here
of what they look like when they're growing.
Okay, so that's the backstory.
The real story is that we've been studying these a long time.
And we use lots of techniques
and when we're getting ready to do electron microscopy
with these guys, we dry them in air.
We stick them in a vacuum oven.
And then we put them in another vacuum system
and coat them with gold and palladium
so that they're electron dense.
And then we throw them into the electron microscope
and we zap them repeatedly with electron beams.
High-voltage electron beams.
And I was looking at some of the older samples one day,
and thinking we need to do some more images--
'cause eventually we'll live long enough
to publish this stuff--
and so I pulled out some of them and I thought,
"God, they look fuzzy and brown."
And I put them under the optical scope
and sure enough, they were fuzzy and brown.
And I thought, "Oh, no,
it can't be those guys growing up through."
But it is.
They're growing up through-- after all that abuse,
they're not dead like most microbes.
They're growing back up off the stubs.
And now they've done it four times.
I thought it was an anomaly.
We did the genetics on them.
We know who they are.
They're not related closely
to anybody else or a type of fungus.
They just look like ordinary fungus
you'd see in your refrigerator.
But they're not.
Or maybe they are?
I don't know.
But there are organisms out there
that you can't kill very easily.
And this means that they are very robust
within the geological setting.
So we've got guys that are trapped
and living for at least tens of thousands of years.
We've got bugs that you can't kill off by a variety of means.
This means to me that Earth's crust really contains
not only unique organisms,
but organisms that are uniquely tough
and that can persist over very long periods of geological time.
This has implications for Mars, of course,
if you think about changes in obliquity cycles on Mars.
And obliquity summers and springs and things like that.
So part of our practice in going to these extreme environments
is really to practice for how we think about
doing life detection and how we put those missions together.
In our cave work, we're really dealing
with something that is pretty alien.
And I show you some examples of these.
So far, all we can do is see them
in electron microscope pictures.
They look like little mesh stockings.
We actually call them "microcholla,"
because they look like the Cholla cactus skeletons,
except minuscule.
These things are about a half a micrometer in diameter,
a few tens of micrometers in length.
We have chased them all over the world.
They're in just about every subsurface environment
in just about every geochemistry,
every lithology, and every temperature range.
Every altitude, every latitude.
They're all over.
Maybe they're coming to get us,
I don't know, but they're really slow.
So that's the good news.
And we can't match them up with the genetics,
because I can't grow them.
And when you do the genetics of an environmental sample,
all you get is this giant dance card
with a bunch of strain numbers.
So we see them, but we have a logical disconnect
about how to put those together with the genetic information.
I've shown these to every kind of microbiologist,
and plant biologist and animal biologist I know.
Nobody has a clue.
So right here underneath our feet on Earth we have,
essentially, what amounts to aliens--
that we cannot easily figure out who they are.
It's some kind of life-form.
We don't know.
So I just want to end up with a couple thoughts
about the role of exploration and its danger and risk.
You know, we go into these dangerous environments
not just so we can go into dangerous environments--
it's not a, you know, extreme sports show.
There really are fundamental,
scientific reasons for doing this.
But the exploration itself, and the fact that there is danger,
actually brings another flavor to the science
that I think can be missing
if everything is tremendously safe.
The danger itself really focuses the mind,
and we put up with all of these things
that I show here, you know--
we have to cope with atmospheres
that we personally can't breathe.
Great heat or cold, you know, rocks are falling on you,
who knows what-- your gear is failing,
everything is going to hell in a handbasket.
You know, this is expeditions, okay?
So that's annoying.
And you want to minimize the danger.
But in a way, it really does focus your mind.
It really immerses you in the environment
in a way that is very hard to do in another way.
And this is something for us to be concerned about--
about how do we bring that flavor of true human exploration
as we try to develop robotic devices to actually help us,
both here on Earth but also in extraterrestrial environments.
The exploration alone is not enough.
You have to couple that then
with the rigorous discipline of science,
which is not an easy field
as a lot of you folks are finding out.
When you put those together,
this is where the understanding emerges,
and this is really the query that we're after.
So all of the work that we and other folks
in our field of astrobiology do
is really focused on this elucidation
of those three questions that I posted at the beginning.
What is the origin and evolution of life on a planet,
in a planetary context?
Who are these guys and can we find them,
can we recognize them?
And ultimately, what happens to life in a universe?
What happens to life in our universe and our galaxy?
So with that, I'll end up with a bat.
Okay. Thank you, guys.
[applause]
- So we have time for a few questions.
If you have a question, please raise your hand,
wait for the microphone, and then stand up,
ask your question.
Thank you.
- Hello, so I don't know how easy it would be
to quantify this, but when you look at the environments
in the caves, would you say that there's a particularly higher
or lower concentration of microorganisms there,
compared to other environments on Earth?
- There's a higher diversity.
The biomass depends on the energy sources.
So in some caves, like the sulfuric acid cave,
because it's got all that yummy hydrogen sulfide
that everybody is grooving on, it's dripping.
It's massively biomass-rich.
When you go into other caves
where you don't have that extra enrichment,
where they're either competing for tiny amounts of organics
that's actually in the bedrock,
or they're making their living
transforming manganese or iron or something like that,
then there's much less energy.
So the total biomass is less.
So the answer is yes and no, and it depends.
Okay.
Come on, you guys.
- Penny, that was fascinating.
Hi. I'm here.
I have a question for you about the depth--
the depth that to which the organisms will extend.
The Earth heats up at about 25 degrees per kilometer
in non-spreading zones,
which means at 10 kilometers we're at 250 degrees Celsius.
Way, way, way beyond what anything can live at.
So the Earth is sort of naturally sterilizing itself.
And there's also, of course, radiation damage.
How do you account for this?
- Well, I think that there are complexities.
First of all, the geothermal gradient is not constant.
So there are variabilities.
So that has to be taken into account.
Secondly, there are organisms that are known
to be able to grow at 122,
but it hasn't been pushed much beyond that.
But a lot of that is actually operational.
It's very difficult to work under very high pressures
and high temperatures in a standard laboratory situation,
to actually test whether some of these organisms
can tolerate high heat.
There have been anecdotal reports of organisms
living in and around the hydrothermal vent smokers
at much higher temperatures.
The issue is how do you actually, you know,
demonstrate that in a rigorous fashion?
That has not yet been done.
There are probably things that get you before the heat.
And one of those very important things
is just the living space.
So at some point, the lithostatic pressure
of the overburden becomes so high
that you essentially squeeze out all the living space.
And so I suspect that in many cases,
that actually occurs before you get to the cooking temperatures.
We don't really know very well
what those cooking temperatures are.
But there are geothermal highs and geothermal lows and so,
I would expect that where there is much lower geothermal flux,
that you would have the potential
for organisms penetrating to a greater depth.
But we know.
People are getting them out of five kilometers.
So at least at that level, we know
that this is a lot of the South African gold mine work.
But there are cores that have been done deeper,
to seven kilometers,
where there is still some microbial activity.
So, you know, exactly how deep that goes, we don't know.
And it leaves you to speculate, you know,
what happens on another planet
when you have a lower gravitational constant?
I would expect the potential depth of penetration,
just on the basis of the lithostatic pressure alone,
to actually, maybe, extend deeper into the crust.
So it's a fascinating thing to contemplate,
and we have way too little information
to really give a definitive answer.
- Have you had sampling problems because of contamination?
- Oh, absolutely.
Huge sampling problems, the gentleman just said.
With drilling, there's huge sampling problems.
This is why caves are so wonderful.
And in fact, even mines,
which I think of as anthropogenic caves,
are wonderful because even though
they're dirty environments and impacted by humans
and their contaminated equipment,
at least it gets you down far enough, you know,
into the system that you have at least reasonable control
over drilling from that point.
So it already gets you some significant depth
within the crust, and then you can try to bring to bear
better sampling controls to eliminate
or, at least, control or identify contamination
than you have if you're drilling right from the top.
- Back here.
Up here.
What to think the prospects are
for your research influencing the search for life on Mars?
- Well, I'm slugging it out. [laughs]
I mean, I don't know.
There are a lot of contenders.
I have to say that in terms of the Martian surface,
it's a pretty unprepossessing surface,
you know, as far as we know about it now.
So, you know, in my view,
you've got a couple places to look.
On Mars, you can go in the subsurface
either by accessing natural cavities,
or by drilling-- which, you know,
only people who have never been on a drilling rig think is easy.
Or you can possibly go and interrogate these
newly-confirmed-as-liquid-brine recurring slope lineae,
or you can focus on the poles, perhaps.
So it's one of the contenders.
For looking for ancient life, you know, it's a different game.
There's probably a lot more places that you can look,
but if you're actually looking for living or perhaps recently--
"recently," whatever that means--
deceased life, then I think
that it's one of the leading contenders.
I think that when you're looking at icy moons
with liquid interiors, you're looking at a cave.
So, I mean, you're looking at a cave situation.
And so I think thinking about it in the framework
of being in a cave is just sort of a natural connection.
- You mentioned different chemistries for energy sources,
but is water still a necessity?
- Yeah, I mean, water is a necessity
in the organisms that we have studied.
On the other hand, I don't know that we have
the techniques or mentality
to reframe the question
and I'm not sure that anybody is really looking for life
that doesn't have water and how we would--
so many of our techniques of analysis and detection
are dependent on the fact
that we're looking for the aqueous chemistry.
And we're looking for things that we recognize.
And if it was really a different kind of life-form,
it would be very hard for us to detect it.
So, I mean, it's a very difficult question.
I wouldn't rule out that there are potential life processes
that might happen when you don't have water.
It's just I don't know how to look for them or study them.
- Thanks for a fascinating talk.
I was just wondering, given your work on microbial resilience,
do you think our planetary protection principles
are currently sufficient to stop Earth life
from contaminating potential sources?
- You know, I've just come off serving for nine years
on the Planetary Protection Subcommittee
and I care about it a lot.
And I think we need more work.
I think that Planetary Protection is doing what it can
with the cadre of tools currently at its disposal,
but really there has been a lack of resources
put into innovative methods of sterilization,
or other ways of controlling potential contaminations,
so I think it's an arena in which we have much to do.
Do I think that it's adequate
for some of our current mission purposes?
Yes, I do.
As long as the protocols are stringently applied,
but it's not the end of the story.
And it's been very frustrating to see that,
while other areas of research in astrobiology
and elsewhere have been given the resources that they need
to actually advance,
the Planetary Protection has been the poor stepchild of this.
But it is a critical need that we have.
We must be assured that we're not just detecting Earth life
when we are doing life detection,
and then for missions like sample return,
it's very critical that we not return
anything even astronomically unlikely
to create any kind of problem here.
And I think that the risk is not zero,
although it's very small,
because pathogens and hosts tend to co-evolve.
And so, you know, but it's the only home planet we have.
So it's an area of great concern to me
and it's an area of concern to astrobiology,
because we want the science to have
the very highest fidelity that we can.
- Very, very cool talk.
I think we've been sort of dancing around the subject
that these are not isolated from the surface community,
because it looked like in an awful lot of pictures
that people were breathing.
So obviously, the oxygen's getting in from the surface.
And, you know, I think much the same is said for the deep ocean,
the organics, so it's not divorced
from the photosynthetic world.
So my question is, could you really have a cave ecosystem
that's completely sealed off
and have you looked at transfer of microbes and so on
back and forth to surface?
- We actually do have some systems
that are completely anaerobic.
And at great depth.
The reason I don't show pictures of them
is that we have to use other techniques,
and we're just-- we're not in there.
You know, there are very high CO2-containing caves,
for example.
Now, the truth is that I think that it is impossible
to make the argument that you have any environments on Earth
that are truly, completely
uninfluenced by surface processes.
Because, you know, we've been thoroughly invested for what?
4 billion years or something like that.
You know, plus or minus a few hundred million.
And it's like the planet is a product
of this interaction of the geology and life.
So we have no clean controls here.
All we can do I think Lynn, is approach it with that in mind--
that there really are caveats in all of these systems.
I actually think that you can run a system
without that surface influence.
It would be a very low biomass system,
probably at a very slow pace of life.
Very much lower primary productivity
than we're used to here.
But not lower than we see in a lot of these environments.
I think that some of the South African gold mine work
is maybe the closest you can get.
That's a fascinating study,
whether the macroscopic organisms that they're finding,
the worms, are really indigenous
to that subsurface environment. I don't know.
- Well, their ancestors were aerobic, so--
- Yeah, right. I mean--
- Could you ever really have a primary system and therefore--
- I don't know.
I think it's impossible because of this, you know--
we are a hysteretic system.
I mean, we can't escape the history of our planet.
And we're trying to look for a completely sealed control.
I just think it's ridiculous to claim that we're seeing it.
I think all we're doing is trying to approximate that.
And, you know, in the spirit of full disclosure,
we have to point out all those caveats
and then try to find ways
to correct for them in our thinking.
I mean, we're gonna go look on Mars for these, right?
And that's where we're going to find
whether or not this is possible.
And I think here, you don't want to overclaim the evidence.
- Here. Up here.
- Hi. - Hi.
Thank you very much for a very inspiring talk.
You mentioned your efforts for DNA sequencing.
Now, you didn't tell us much about the results.
What did you find?
- I only alluded to the results,
which is we find tons of everything.
And you know, to give you the broad-brush picture,
almost nothing that we find--
unless the cave is very, very shallow
or has an active surface stream running through it,
which, you know, occurs in Tennessee and other places--
almost nothing we find is very closely-related
to anything that we know.
So we're looking at an almost entirely novel community
or set of communities.
The patterns that I think are the most interesting,
that I hope that over the next century
people will do more and more work
on these subsurface phylogenetic relationships,
what I actually think I'm seeing
is the fact that we are looking at indigenous organisms.
And that their closest relatives are far-flung around the globe.
And what that says to me is that
they are permanently in these chunks of rock.
And that the transport mechanism is not the usual ways
that we have on the surface,
by water and wind and so forth,
or you know, hitching a ride on an animal or something,
that we are looking at the results of these chunks
of real estate being dragged around by the--what is it?
Hundred-million-year, 500-million-year
supercontinental cycles.
I actually think they're permanently in the subsurface.
I think they get dragged around with chunks of continent.
Some of them are lost by subduction.
But enough remain that they are the founder's stocks,
so that they reemerge evolutionarily
when you get an intrusion into the subsurface
like rock fractures and caves
and, in fact, human mining activities.
All then allow an increasing rich--
niche-richness to occur
in those invasions into the subsurface,
which allow those founder organisms to flower once again.
This is the only uber hypothesis that makes sense to me.
I don't expect to live long enough
to see this tested reversely.
Which is why it's so much fun to say it, you know?
'Cause I don't ever have to suffer the consequences.
[laughter]
- So with that, please join me in thanking Dr. Penny Boston.
[applause]
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