Part 2: Gravity Assist Podcast – Earth, with Tom Wagner
The Gravity Assist Podcast is hosted by NASA’s Director of Planetary Science, Jim Green, who each week talks to some of the greatest planetary scientists on the planet, giving a guided tour through the Solar System and beyond in the process.
This week, he spoke to Tom Wagner of NASA’s Earth Science Division, to discuss NASA’s work studying our planet. In this second part of their discussion, they look at some of the technology being used to study the environments at Earth’s poles, the role that volcanoes play on Earth and what it’s like to work in Antarctica.
Here’s a condensed version of the podcast.
Jim Green: What are some of the new tools that are being used to study the polar environments?
Tom Wagner: There’s three different flavors that I think really cross over with planetary applications right now. We’ve actually been developing robots that will drive great distances across the ice and make measurements, [for example] by dragging radars behind them to map underneath the ice, and we’ve got some that have travelled a thousand kilometers already, and it’s really a promising area for us because these areas are just so remote and so challenging and so dangerous to work in, and you need precise, accurate, high-resolution information that only a ground survey can provide in some cases. So, robots have really great potential for us.
We also work in the air. Unmanned aerial systems are things that we’re using now over sea-ice and land-ice at all scales. In some ways, some of the most amazing research is going on with small aircraft where people are using those to map surface in a range of ways.
Then, finally, undersea exploration or under-the-ice exploration is really one of the next big areas where what we need to do is understand the flux of heat between the ocean and the ice to understand why it’s breaking off, melting and going to the ocean so fast. In some of those places you can’t go up next to them with a boat because an iceberg the size of the US Capitol Building might calve off [shed smaller icebergs] on you. One of the only ways to do it is with submersibles that are autonomous. Under the sea-ice in the Arctic, you need to be able to go great distances and make all kinds of measurements, [meaning that] just like in the planetary science case, where you need to operate in a remote location with something that’s got some autonomous behavior, that’s what we really need, too.
Jim Green: Your work at MIT where you graduated was on volcanoes, not only on the Earth but also on the Moon. How do volcanoes play a role in the conditions here on Earth?
Tom Wagner: Volcanoes are really important. They affect us through natural disasters, but on top of that volcanoes refresh the soils by bringing up all these nutrients, creating great soils to grow crops in, so a lot of the time they are great places to live because of the soils. But they also really fundamentally affect the composition of our atmosphere. They constantly release carbon dioxide (CO2) into the atmosphere, which can cause the planet to warm, but they can also can throw particles into the upper atmosphere, which causes the planet to cool.
For us trying to understand the Earth as a system, the effects of volcanoes are so great that if you want to do something like interpret the Earth’s temperature record, you have to understand what input volcanoes had. And every couple of decades we get a massive eruption that really changes the planet, it might even make it cool for a couple of years.
Jim Green: Well, volcanoes also generate a lot of CO2, isn’t that right?
Tom Wagner: They are constantly releasing CO2 into the atmosphere, and if you think of the billion year cycles that occur on the Earth, volcanoes are the component that drive CO2 up. Then it’s weathering of rocks: as rainfall comes down, it scrubs CO2 from the atmosphere [and] that CO2 reacts with rocks, and it actually produces things like what critters secrete, like the Bahama Banks [limestone – or carbonate – platforms below the water around the Bahamas] and other processes through that. The volcanoes bring the CO2 back up when it gets drawn down [into the mantle].
One thing to understand is that the scale of that process is so profoundly slow compared to what we’ve done as humans, it operates on tens to hundreds of millions of years, compared to what we’ve done in a pretty short time.
Jim Green: The volcanoes here on Earth and the release of CO2 and other particulate in the atmosphere remind me of Venus and what we think may have been happening there for so long, and that is it is very volcanic, there’s still some hot areas on it, and it may still be releasing an enormous amount of CO2. So, what’s the difference between Venus and Earth when you look at it that way?
Tom Wagner: One of the things I love about Venus is that we see these funny volcanic structures, like these haystack things. And, as I understand it, some of the fundamental ideas for thinking of the Earth as this greenhouse came from studies of places like Venus. But, also on all the terrestrial planets, a lot of the processes that run on those, on the Earth and on Mars and on Venus and even the Moon, are pretty similar, like the fundamental processes by which you create magma and what the composition of that magma is.
Now, the planets have slightly different histories because of their different compositions, but the overall principles that govern them are the same. That’s why you’ll find that a lot of the time scientists who study volcanoes on the Earth also study the other planets, too.
Jim Green: I’m constantly being reminded that what happened on Venus can happen on Earth, and so we need to study these terrestrial planets and understand their evolution because we’re all evolving, even today.
Tom Wagner: Yeah, good point. And I also think that what I want to say to kids and people who are [reading] is that Earth sciences, planetary sciences, they’re really fun detective mysteries and they’re just kind of inherently interesting. Like, ‘hey, we found this weird looking volcano on Venus, what the heck made that?’ How would we go about understanding that? What kinds of things would we do in the laboratory? What kinds of places on Earth might we explore to sort of understand that? And then, ultimately, what kind of mission can we fly to a place like Venus to try to understand it?
Jim Green: So, what’s coming up next in Earth science in terms of the satellites or the missions or the real important themes to study?
Tom Wagner: We’ve got a couple of great missions coming up in the coming year or so. The GRACE follow on mission is going to occur. The GRACE mission was a pair of satellites that orbited the Earth, very precisely mapping variations in mass, and they’ve been used to do everything from figure out how much ice we’re losing from the big ice sheets to understanding how there’s a cycle to the way water is stored on the land that is so great it even affects sea level. So, that [follow up] mission will fly – I think it’s gonna launch in May 2018. Then later in the year, towards the fall, we’re going to launch ICESat-2, which has LIDAR [LIght Detection And Ranging]. Think of it as a laser altimeter in space. It’s a very special one, though. It’s going to have six beams mapping the height of the Earth all over and in particular we are going to look at the thinning of the Arctic sea-ice. We’re looking at the change in the height of the ice around glaciers and ice sheets around the world, and we’re also going to map the height of all the trees on Earth with an idea of figuring out how much carbon is tied up in all the terrestrial biomass.
Jim Green: It’s those kinds of fundamental measurements that can provide us with an enormous amount of information about the Earth and understand its biosphere and how it changes over time. So, I’m really excited about those upcoming missions and the technologies that are developed for Earth science missions can indeed be very important for planetary missions, too.
Tom Wagner: Oh, yeah, it’s a lot of the same kinds of sensors and it’s the same technologies that you apply to both places. I think with planetary science, we have this additional challenge, because [the planets are] far away. But one of the other amazing things that I think people forget about, and the problem with the Earth, is we’ve got this great atmosphere with clouds that protects us in a lot of ways, but it’s tough to see through. So, you get a little lucky with some of the other planets that don’t have [a thick atmosphere].
When I worked in Antarctica and I was in the Dry Valleys, we would go out and map some of the local rock glaciers. Those are places where there is rock held together with ice that was slowly flowing. Whilst there I met some of scientists who study Mars, and they got some of their ideas for interpreting pictures we had of Mars from working in the Dry Valleys with some terrestrial scientists.
Jim Green: What’s your favorite image of the Earth from space?
Tom Wagner: Ooh. I think that my flat-out favorite one is where we combined some Landsat images together to produce a map of Antarctica that showed amazing blue ice flowing around rocks, and you could actually see the deformation structures in the ice. It’s also one of the areas where we found the meteorites that we think came from Mars, so there’s a good planetary connection too. But, that’s one of my favorites.
Jim Green: Indeed, from a planetary science perspective, Antarctica is just a fabulous place to look for meteorites. We go down there every summer, line up a series of snowmobiles, track across the glacier, and it’s blinding white because of the reflected light off the snow, but [every now and then you see] these black areas, and you go to them and there’s a meteorite. We tag them and bring them back, and sometimes, we’ll bring anywhere from 600 to 900 back each season.
Tom Wagner: As they always said to me, if you’re out in the middle of nowhere on the ice and you see a rock, you know it’s a meteorite.
Jim Green: You know, one of the iconic pictures for me as a planetary scientist is the one that Carl Sagan had Voyager 1 do. It’s called the Pale Blue Dot. Do you remember that?
Tom Wagner: Yes, and for me, that picture of the Earth, so tiny, so far away, it’s really important for putting things in perspective. One of the things that I’ve always loved as a scientist and someone who’s crossed into planetary science a little bit from Earth is the cosmic zoom idea, the idea that sometimes here on Earth, we can get narrowed down to looking even at nanoparticles and smaller things in any part of the Earth’s system. But, you pull back sometimes and think about how, here we are as part of this kind of larger Galaxy and Universe and processes that happened in stars [that explode as] supernovae have even generated the little bits of iron that are in our body, and it’s all connected.
Jim Green: One of the things that I ask each of my guests is what their “Gravity Assist” was – that activity or event that occurred that really propelled you to become the scientist you are today. So what was yours?
Tom Wagner: My mom says that, when I was a little kid, I grew up with rocks in my pockets, and she was always taking them out before she put them in the wash. I knew I wanted to be in science, I was the kind of kid that always had microscopes and slides and was doing things. But, I think really when I got to college and I took my first Earth sciences class in the 1980s, it was in that period where we were switching from an ‘old school’ kind of geology to ‘new school’ Earth processes, and I had a really great professor, Tim Lowenstein, who still teaches there, who was like, ‘Hey, man, the Earth is this great big interconnected machine, and we’re trying to understand it,’ and that was really the thing that gave me my sort of pull to get into the field.