This is geology B with Oliver's trampled.
While Mars has been visited by several missions over the past
few decades, Venus has seen very little exploratory activity, but
in June 2020, 13 missions to Venus got the green light to
from NASA and one from the European Space Agency.
One of the NASA missions is called Veritas it will create
integrated global maps of the topography radar, reflectivity
gravity field and rock type for the venusian surface.
It is the first mapping mission to Venus since the Magellan
mission in the early 1990s. Soos Rekha is the principal
investigator for the Veritas Mission.
She has been part of multiple NASA.
Planetary Explorations, including the previous one to
Venus Magellan, and the Insight robotic Lander on Mars sushma
car. Welcome to geology B.
Thank you, thanks, for having me.
It's only a few months since Veritas got approved.
Can you give us an overview of the mission calendar from here
on out? Out.
Sure, the timeline we anticipate is to launch in December of 27.
It takes about six months to get to Venus and then we have two
phases of aerobraking where we slow down using the atmosphere,
put our solar arrays into the atmosphere and use them
basically as break so aerobraking.
So we do that. For a period of six months we
interrupted and we do have another period of 10 months in
that interim time period. We are in a pretty elliptical
orbit and we can use our spectrometer from that altitude
to acquire data for the surface. Once the second phase of
aerobraking is complete that will be in early twenty Thirty,
we will then start our full science operations which will
continue for three Earth years and that's basically for Venus
Cycles. Be useful, fully spin underneath
us four times during those three Earth years.
So, when you're in this highly elliptical orbit, Will you be
telling off the aerobraking so that you can use the
spectrometer? And then when that phase of the
mission is done switch the solar panels into their breaking
position again and go down into your lower circular orbit rate.
During the time when we're taking the spectrometer data, we
he's out of the atmosphere a little bit and that time, period
is chosen because it covers conjunction when Venus is in the
other side of the sun, from the earth.
So, I have a hard time communicating to the spacecraft
so we don't want it to be in any position where it could get
itself into trouble. So we pull back a little bit
from the are breaking so we keep it in a stable configuration and
we take advantage of the fact that we can take good data with
our spectrometer during that pause in the aerobraking.
And then after that phase, when you go into the circular orbit
is the main point to get closer to the surface.
So you're mapping activities will have higher resolution.
Yes, so the final orbit is a trade-off between having too
much atmospheric drag that we have to be constantly adjusting
the spacecraft and keeping it from crashing into the surface
if you will. So we wanted to have a stable
orbit but as low as possible and that supports the
high-resolution data that we acquire from our radar
instrument and for our gravity field, what are the main
scientific questions that Veritas will seek to answer
Primary three are understanding how rocky planets evolved.
Another is understanding, what processes are active on the
surface of Venus today. And the third one is looking at
the influence of past and present water before we go into
more detail, about how the mission will shed light on the
scientific questions. Let's talk about the instruments
on board the spacecraft. Okay.
So we have to Two instruments and this gravity science
investigation. So the radar has just one radar
way that we propagate outward but depending on how we process
it it gives us lots of different types of information.
The timing of the return of the radar signal tells us about the
topographies, we directly measure the timing and get the
height of the departure fee, how the radar waves scatters as it
returns tells us about the surface properties.
How Scattered on the surface has to do with the roughness and to
some degree. The composition of the surface
at the wavelength of the radar. So around several centimeters
that's what makes up the radar image.
So the rougher the surface, the more of the radar signal will be
bounced back to the spacecraft and so it will look brighter but
if it's smooth the signal might just bounced away and you won't
see anything to look dark. So that's how the surface
texture. Has an impact.
What about the surface composition?
You just mentioned that that can make a difference as well,
right? So if there's a kind of
metallic, if you will type of material at the surface that
also will cause the radar wave to be reflected back more
strongly what we've seen in the Magellan data is there's
something called a Snow Line and Venus which sounds a bit crazy.
But that term is used because it corresponds to an elevation
which corresponds With temperature and we've seen
evidence of perhaps ferroelectric minerals at the
surface and there's a lot of debate and argument as to what
that could actually be. But there seems to be a
variation that corresponds to temperature differences that
cause the minerals of the surface to be more or less
reflective. In some places, the difference
in the reflection corresponds to very nicely to the elevation in
other places it seems is to not exactly reflect the elevation
suggesting that it's not yet fully in equilibrium, so people
have suggested imply recent activity so that the chemical
reaction is not fully gone to completion.
So it could be a place where there's relatively recent
volcanism. So is Venus a bit cooler as you
go further up in elevation, just like the Earth.
And are you suggesting that there for these conductive
materials are not stable. At the higher temperatures and
kind of have evaporated and therefore they can only exist as
ferroelectrics know if you like on top of the mountains.
Yes. Exactly.
They don't necessarily evaporate, but the near surface
coating will change. So the minerals right at the
surface will change slowly as the chemically interact with the
atmosphere at a given temperature.
So Magellan also have a radar instrument, how does the Veritas
instrument compared with that on what?
Yellen and what kind of different mapping result?
Where we get Magellan was an s-band radar?
Veritas is X band. So we are a slightly shorter
wavelength and we decided to use that wavelength to focus on
producing the highest resolution.
Topography data set that we could.
It also will give us good radar Imaging but there's a big trade
space of what Radars will operate on Venus, do The
atmospheric attenuation and what wavelength is optimal for
different types of data sets. And we decided to optimize to
produce topography to our best ability and what kind of
resolution can we expect? Well, we'll have two orders of
magnitude better, topographic resolution relative to Magellan.
So Magellan is about 15 to 25 kilometers per pixel in
typography. Veritas will have 250 meter.
Or pixel size with 6 meter, vertical Precision.
So if you imagine Hawaii we have a few dozen pixels and Magellan
resolution so you can tell that there's a topographic hi there.
With Veritas we will be able to see calderas fracture systems,
individual lava flows. So the detail that will get in
the topography will just be exquisite.
Every time we have explored a planet with an order of
magnitude better resolution, we have just uncovered features
that we had no idea existed there.
So I am ready to be fully amazed as to what we may discover on
the surface of Venus, when other type of data that we will
acquire or the radar, and that is surface deformation.
This is the first time, we will search for active surface
deformation using radar On another planet.
Again, the resolution that will be able to get is just
incredible. We will have the ability to see
vertical deformation on the scale of a couple centimeters
over km horizontally. So we can see if a Caldera above
a magma. Chamber has moved, we can search
for active faulting, that's fantastic.
So it will be on successive passes over the same part of
Venus. So the orbit is fixed in space.
Space. And the planet is rotating
slowly below it. And when it comes back to where
it was before, which his 243 days, you'll be able to get
another measurement. Is that how it works to first
order, but to take this kind of data, we need a higher order
Precision. So we actually have to adjust
the path of our spacecraft very carefully to get in exactly the
right spot to reacquire this data because any differences.
In the position of the spacecraft could be
misinterpreted as defamation. And so we actually have 160 m
tube. If you will, that we have to fly
our spacecraft through in order to be close enough to the exact
same position that we were in previously.
So even though in general, our spacecraft does come around
again to the same place that's on the scale of a kilometer or
two. Is that a navigational challenge
for the rocket engine people? Yes, yes.
Navigators, Of this kind of challenge.
I bet. Good old NASA.
JPL Ingenuity at work here. So let's talk about the other
instrument, which is called the Venus emissivity mapper.
Yes. A couple of decades ago.
People did not think you could observe the surface of Venus
with a spectrometer through the very thick Cloud layer and the
den, CO2 atmosphere. However, a couple of missions
have shown that that is possible.
Galileo flew by Venus With a spectrometer that included the
band's year 1, Micron and was able to get the first hint of
the surface beneath the cloud using spectral measurement and
that was followed up by ethos Venus Express Mission.
Although they are spectrometer was not designed for that
purpose. They were also able to take
observations of the clouds that we need to do part of the data
processing and a relatively narrow band near 1 Micron 1.02.
Microns, which is in the infrared portion of the spectrum
and they showed that they could map, variations in that
wavelength on the surface related, primarily to
composition and our spectrometer, the Venus
emissivity mapper is the first one that is fully designed to
optimize observing the surface of Venus.
But our instrument has six bands right around 1.
Micron those are the only ones where you can see through the
CO2 atmosphere Fortunately, for us, that area is very active for
iron mineralogy, so that the iron two plus iron three-plus.
That's where the absorption features are for various iron
minerals and although we don't have such a broad part of the
spectrum. We say, okay, this is a given
mineral. What we can do is get at the
overall iron content and that's just really important for a lot
of fundamental Questions about the rock type on the surface of
Venus, you can also use it to address.
This question of whether or not there are recent volcanic flows
in the surface, Venus Express size, 6 or 10 different
locations, where there's High emissivity of the surface and
that's consistent with relatively fresh Basalt on the
surface that has not chemically interact with the atmosphere
fully. And we'll also be looking for
thermal flows. Things are actually incandescent
on the surface recently. Erupted.
We have to be very lucky to catch active flows with our
spectrometer because as soon as a flow comes out of the surface
it cools at the surface forming a crust.
And so the time period during which a typical flow has
incandescent, glow is relatively limited on the order of weeks
typically the Venus emissivity map a I'm like the weight off is
a passive instrument and it's just the examining the surface
looking for its emission. In this near infrared band
around 1 Micron. So you're going to basically get
out of this. The global near infrared map.
I suppose. What spatial resolution will
that map have? Well, it's quite low resolution
compared to most spectrometers. It's limited to 50 60 kilometers
because that is the height of the cloud layer.
And there is absorption of the signal in the cloud layer.
And we have to do data analysis to take out the effects of the
clouds but were limited By that scale of the cloud height but it
will be the first-ever global, look at composition.
So you also mentioned a gravity experiment and that reminds me
of an earlier podcast in which Dan, Mackenzie talked about
using accurate measurements of the orbital velocity of
Magellan, to measure the gravity field and he used that coupled
with a topographic map to determine something about the
interior of Venus, will you be doing a similar?
Experiment with Veritas yes, very similar.
We will be improving on the resolution for Gravity by a
factor of two or three basically gets us down to 150, ish
kilometer resolution and that's very important for understanding
the elastic thickness which is the topic you are speaking to
Adam Mackenzie about. So we will be able to much more
precisely see defamation of that elastic lithosphere reflected in
the gravity and topography so I'm very excited for that
measure. As well.
Okay, so now that we've discussed the instruments and
the gravity experiment and the kinds of data that you'll be
collecting, let's talk about how these data bear on the
scientific questions that you mentioned earlier.
And let's start with the processes that shape rocky
planet Evolution. We are basically going to be
studying the tectonic and Volcanic processes expressed on
the surface of Venus and Those processes give us a window into
what's going on inside the planet.
They give us a sense of how the interior shapes the surface and
how that is contributed to the evolution of the atmosphere over
time. For example, one question is Did
Venus catastrophically resurface or has it been steadily
resurfacing over time and by re service, what I'm really talking
about is what happened to the impact craters on the surface of
Venus? If you look at the moon or Mars
or Mercury is littered with impact craters, Venus has only
about 1,000 that tells us that it is a young surface.
How young is a matter of debate? It could be on average as little
as 150 million years on the far side.
It could be as much as close to a billion years on average, but
perhaps the bigger question is, what happened to all the prior
impacts? You know, if you look at the
surface of the Earth, you don't see very many impact craters.
Now, we have very different processes in the sense that our
Roshan is a dominant process and sedimentation, the dominant
process. Earth, not so much in Venus, so
many impact craters are, simply eroded away, but still the
surface of the Earth, especially the oceanic lithosphere is quite
young. At most, its 200 million years
on average about 50 million years.
And so the surface of Venus the age is more similar to that age.
Which really says it's got to be an active Planet.
So what's wiped out the impact craters and when there are two
competing models one is the so called catastrophic model.
And that says, there was some Some massive event.
Let's call it. Volcanism influence, volcanism
the surface would have been covered in a kilometer thick
layer at least of volcanism globally the whole planet.
So you can imagine that. That is an entirely different
geodynamic regime than anything. We've seen on the surface of the
Earth, that's just mind boggling and both G.
Dynamicists and climate scientists.
Love this idea. It blows your mind.
How do they plan to do that? What would it have done to the
climate? Suggested that something was
happening in the interior. That was just quite unlike the
Earth, and it would have produced very massive changes in
the climate hundreds of degrees rapidly in the atmospheric
temperature. Another model shows that if you
have small patches of resurfacing, again, let's call
it volcanic because that kind of makes sense for Venus, that you
have volcanism covering up impact craters on scales of a
few hundred to a thousand ish. Hers that fits the data just as
well. It's not quite as dramatic, but
it fits the data just as well. And if you've taken other
factors such as the distribution of extended ejecta, the very
fine-grained material, that gets projected into the atmosphere.
When a meteor hits, the surface, those features are huge on.
Venus say they can be as long as 2,000 kilometers there, the dust
and small particles gets carried down wind.
We can see those in the Magellan data.
So if you take into account how those have been disappearing,
that also points towards a more steady process of removal of
craters, and there's all kinds of new data suggesting that
there has been recent activity on the surface of Venus.
The Venus Express data, I mentioned people have also
looked again at the Magellan, snowline information that I
mentioned and there's also variations in the composition of
the atmosphere, the concentration of sulfur dioxide
as Very dumb timescale of years, a decade.
So that could be coming from volcanoes in the surface.
So, I think this Paradigm of Venus having catastrophically
resurfaced that thing that you typically read in textbooks is
really changing. So that's a question that will
very precisely address by looking at the distribution of
volcanism particularly in and around impact craters, with the
infrared data. Mainly well, a combination one
of the big questions that will address This is what's the dark
stuff radar dark stuff at the bottom of 80% of impact, craters
on Venus, it's dark. So it's smooth.
Is that material? That's filling those impact
craters? Is it volcanism or is it alien
material? That's gotten trapped inside
those impacts. If you look at impact craters on
Mars, they're just full of dudes because the dust gets in there
and it can't get out this and that could be the case for
Venus, but some preliminary studies.
Is suggest that the dark floors and Venus are actually volcanism
and that's based on the fact that if it's volcanism, you
would expect to see not only that the impact crater floors
would be shallower, but outside of the rims, you would also
expect the volcanism to be flooding around the outside of
the volcanoes. And it's just hard to be
completely definitive about that with the data that we have now.
So not only will be able to use the image data to see.
Does it look like a dune? Doesn't look like a lava flow?
But will be also be able to see how the impact craters are
flooded. If it is vulcanism, when you
mentioned the idea of a catastrophic resurfacing of
Venus, I was reminded of a previous podcast with Peter k
word in, which he talked about a possible catastrophic.
Overturn of a stagnant lid on Earth sometime before plates.
Formed, are you saying that the evidence suggests that such an
event? Probably did not occur on Venus,
yeah. What type of geodynamic
processed? Use have, it's a very high-level
question. I said, volcanic resurfacing.
But another idea that people have had is that the entire
lithosphere somehow became gravitationally unstable and
sunk into the mantle. So lithospheric overturn, a
recent study, looked at the relationship between the gravity
and topography and suggested, that that really didn't make
sense. Because if you had massive
amounts of the cold lithosphere, having sunk through the mantle.
So the core-mantle boundary That would produce signature the
gravity that we don't see. So could that have happened
billions of years ago? Maybe but that would have been a
different event than the one that is purported to have wiped
out impact craters. So that's another reason to
suggest that this catastrophic idea doesn't fit the data well
but in terms of a stagnant lid. Yeah it's a huge question Zhu
Dynamic models. Tended to focus on whether or
not there are plenty. It's moving around at the
surface. That's a first order question
for understanding the Earth. How did these plates come about?
What are the conditions that allowed that to happen?
One thing, I'm super excited about studying is features that
appear to be subduction on Venus and Dan Mackenzie others who
were working on the Magellan data.
Initially, looked at many of these features and said, yeah,
these are very much like some of this abduction features we see
on the earth, they seemed to suggest a similar strength with
his Sphere. They have similar morphology,
that was a big debate again. However others said, wait, these
features are circular, semicircular they look like
mantle plumes. So these are two entirely
different processes, right? One of the key questions that
people studying plate tectonics, 50 years after the original
hypothesis are starting today, is, how did it start?
And when idea is that mantle plumes helped initiate
subduction and this idea of Induced subduction appears to be
what's going on on the surface of Venus.
So we have these curved semi circular arcs of subduction and
that's what's produced when you have plume induce abduction, so
the lithosphere of Venus is very hot because of the surface
temperatures today, and many people have pointed out that
that makes it a good analog for the early Earth when the planet
hadn't cool down very much, so we can go to Venus and look at
this process of plume in do Ooh, subduction and attempt to better
understand the elastic thickness of the lithosphere, whether or
not it's happening today, maybe even see it to forming an
action. So we can really study in detail
a process that probably hasn't happened on the earth for
billions of years. Or if it has happened, it's been
in the context of planet that already has plates so we can
look at in the context of a planet that does not seem to
have plates and try to understand its potential role in
starting the Process of plate tectonics going.
So does vs have a stagnant lid? It doesn't seem to have any
evidence for plate motion, but it may have an entirely
different system. It may have a system that's
going to eventually evolved into plate tectonics.
Those are all questions we really want to address.
Let's move on to the geological processes that are currently
active on Venus. Sure in the Venus Express data,
the locations that we've seen that appear to have recent
volcanism. We are all in areas where
there's additional evidence for mantle plumes on the gravity
data. There's evidence of low-density
material at depth. The Topography is uplifted and
abroad swell like, at the Hawaiian.
Topographic swell, there are volcanoes so far what we've seen
is that the reason volcanism is concentrated above mantle
plumes. So, is that sampling question?
Did we only happen to see that in the Venus Express are Other
types of volcanic processes. That's a really important
question, because where, and how volcanoes form gives us a window
into what's going on in the interior, not only the
temperatures in the interior, but also the volatile content,
the more volatile you have in a magma, the lower the temperature
that it erupts at. So it's important for
understanding the temperature, the viscosity of the mantle,
Also a fundamental question that we're going to answer is or at
least attempt to answer is is water.
Still being released from volcanoes and coming out of the
Interior. Many people have proposed that
the primary difference between Venus and Earth.
Is that Venus is dry. Well, the atmosphere is
definitely dry. The crust is very hot and
definitely dry, but we don't know about what's going on.
In the mantle, some data, even suggest that there may be more
of all tolls retained in the interior of Venus.
Then the earth water has such an important effect on this.
Cos T the mantle and viscosity as a lithosphere, the processes
of atmospheric Evolution. It's an absolute first order.
Question is here, a lot of water still in the mantle.
How would the data give us any clues on the answer to that
question? One of the channels for our
spectrometer is designed to see water in the atmosphere, close
to the surface and the lower 10 kilometers or so of course we I
feel lucky to see that you have to have significant quantities
of water, a few weight percent, shall we say in the magma, which
is observed in some Magma's on the Earth.
But you need that in order to have enough buoyancy for the
gases to Escape Under The Very dense atmosphere of the surface
of Venus. So we'll be looking for that.
Is there any evidence of past water on the surface of Venus?
Some people think there may be evidence of actual fluvial
erosion features on the surface of Venus I think that's still
quite controversial, but I believe we'll be able to answer
that question, much more fully with Veritas, but what number
people feel as evidence for past water is chemical evidence,
basic chemical fingerprint and pass water.
There are very large plateaus on the surface of Venus.
There's about half a dozen. They are in the scale of one to
two thousand kilometers. There are variety of reason to
think they may be analogs of Earth's continents.
The gravity data suggests that they Could have crustal Roots
just like our continents. Do so their so called Isis
statically supported. So just this big pile of
relatively low dense material, and they're highly deformed.
The Veritas will be able to see all of these plateaus will be
able to get out the iron content.
And we think that they may be so-called felsic cross, granitic
crust and our continents is much lower and iron higher and
silica, that's a fingerprint of past water because when you
pray, That massive volume of felsic, trust.
What you need is that melt tons of Basalt, more iron-rich Rock
in the presence of water. You can't get continent, scale
volumes of felsic, rock without water.
So these would really point to the presence of water at or near
the surface. On the time scale of the average
age of the surface of Venus. You mentioned the gravity
experiment and how we'll be able to get a much better handle on
the elastic strength of the surface.
But what about the corn looking deep into Venus?
Absolutely, every Rocky body has a core mantle and crust, it's
just a fact of a planet-forming, very hot and melting and
separating into it's different density layers.
But Venus is a challenge to look at the core using spacecraft
methods because what we are essentially doing is looking at
the wobble of a planet. So now, the classic experiment
is raw egg and a cooked egg. You put it on the desk and you
spin them. And they wobble differently
because of the distribution of mass inside those eggs, same
thing with the planet. However Venus it's kind of a
billiard ball because it rotates so slowly.
It doesn't have hydrostatic flattening that most planets
have. So we need to pay attention to
the wobble. It does still have a wobble but
it's harder to measure than in other places.
We're going to be able to do that.
Well, enough to get the core size 2 plus, or minus 50 to 100
km depending on mental viscosity.
And other things that will tell us, not only something about the
composition of the core, but will also be able to describe
the motion of As well enough to determine whether it has a solid
core as well as a liquid core. We don't know that currently
that's really important for not only understanding the thermal
evolution of Venus but the little bit of insight into.
Why does Venus lack a Dynamo today?
Now all kinds of crazy bodies in our solar system.
Have a Dynamo that we never expected mercury has a Dynamo
some of the icy moons have dynamos.
Dynamos are crazy beasts that are hard to model and It's very
perplexing. As to why?
Venus lacks a Dynamo today. We've now discovered getting on
for 5000 exoplanets. Will a better understanding of
Venus help us understand what it takes to make a rocky planet
habitable and therefore, enable us to refine what it is.
We should be looking for in our search, for exobiology out
there. Yes.
I absolutely believe for going to get important insights into
what makes a rocky planet, habitable.
Well if you were in a another galaxy looking at our solar
system trying to look for planets around our star, you
would have a hard time distinguishing Venus and Earth.
They of course, have different distances from the Sun.
So they would know that Venus is getting more energy from the
Sun, but you would never predict that it has this intense
Greenhouse based on distance from the Sun via should be 50
100 degrees hotter instead of the 900 Degrees hotter It is.
So they look very much identical from a first-order exoplanet
standpoint predicting habitability for planet is a
complex question. And one of the things that I
find very intriguing and compelling is that people are
trying to look at the first order properties of a planet and
say what matters in creating a habitable long-term environment.
And there have been a number of studies trying to get at, er,
Evolution and why it created habitable environments.
What are the important factors? So a number of studies point to
plate tectonics, the formation of continents in creating the
right environment, the surface of the Earth or in the oceans in
particular and there's one hypothesis that says that the
formation of a continents, created a different chemical
composition in the atmosphere basically erosion of continents
dumped, the elements into the ocean that Slyke's that
nitrogen, the phosphorus the oxygen and that the formation of
more continents coincides with the great oxygenation event on
the earth, when by flourished in the oceans and change the
composition of our atmosphere to be more oxygen rich, and Venus
is just a fantastic place to contrast with the Earth and try
to understand what the variables are that really matter.
I noticed you got very excited about subduction zones is there?
Are a potential Discovery or answer to a particular
scientific question that you're anticipating the most.
I think we're really going to just learn so much, you know, on
Earth subduction zones, carry carbon sediments back into the
interior and that's part of the overall climate cycle and it may
be a reason that plate tectonics started on the earth.
It could be a place where there's massive amounts of
volcanism being produced today that could have an effect on me.
Is climate. So yeah, that's the kind of
problem that sits at the intersection of many different,
scientific questions and data sets.
And so, yes, that's one. That's definitely very near and
dear to my heart. Sue's Markov.
Thank you very much. It's been a great pleasure.
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