ASU KEDtalk: Visitors from another world
Gazing at the night sky conjures deep questions about the universe. Meenakshi Wadhwa, professor at the School of Earth and Space Exploration and director of the Center for Meteorite Studies, invites us to look at the planetary ‘Rosetta stones’ right here on Earth that can give us answers.
Meenakshi Wadhwa: Hello, my name is Meenakshi Wadhwa. I am a professor in the School of Earth and Space Exploration and director of the Center for Meteorite Studies at Arizona State University.
I’d like to begin by inviting you to direct your attention to this rock in my hand. What do you see? It looks kind of dark, and to me it feels quite solid, feels heavy. But there is nothing particularly remarkable about this rock and its appearance.
But, here is the thing – if this rock could only tell you where it has been and all the places that it has seen, all the places it has witnessed, it would be the most extraordinary tale that you’ve ever heard! Can you imagine peering back in time almost four and a half billion years ago? Back then our Solar System and planets, including our own Earth, didn’t exist. All that there was in place of our Solar System was a massive swirling crowd of gas and dust, at the center of which was a newly born star, the Sun.
As this massive gaseous disk cooled and the very first solids began to condense out from that, they got quickly swepted up into rocks and looked kind of like this one. And so as these rocks formed, they swepted together to form larger and larger bodies, eventually to form bodies like the Earth. But this rock that I am holding right here, escaped that fate. So literally, it’s a remnant, a left-over fragment from the earliest stage of planet building. It is what we call a meteorite.
All meteorites come from somewhere else in our Solar System. Most of them come from asteroids, but some come from the Moon or Mars. They have traveled billions of miles through interplanetary space until they finally fall on Earth and can be recovered by us. And so it is that I happen to be holding here in my hand, a piece of this rock that I think of as a Rosetta Stone for deciphering the earliest history of our solar system.
So my path to deciphering the stories that are recorded in meteorites began as a little girl growing up in India. I can remember being a really inquisitive kid and asking lots of questions. I was about 8 years old and my science teacher at school, taught us about the process of respiration, that we breathe in oxygen and let out carbon dioxide. I started thinking about this and started to get kind of worried that we humans were using up all this oxygen, putting out this carbon dioxide that must be building up in the atmosphere. So I really got kind of worried about this and aske asked my mother, “Are we going to run out of oxygen? Is the world coming to an end?” And she just laughed and very patiently explained to me the very delicate balance between the abundances of carbon dioxide and oxygen in our atmosphere. And so I came to appreciate early, the beauty and the natural delicate balance in the natural world around me.
I grew up in the shadow of the great Himalayas, and couldn't help but feel awed and inspired by the great forces in nature that formed these tremendous mountains. I eventually found myself in the Geology Department at Punjab University in north India. But I was one of very few women studying this topic in that department at the time. Many of my girlfriends were encouraged by their families to pursue more traditional career paths (for women) like becoming a nurse or teacher. But my parents told me that I can do anything, that I can be anything and while they were really supportive of me, I was actually afraid to tell them what I really dreamed of being. What I really dreamed of being was a geologist, but not just any geologist, I wanted to be a geologist on Mars.
I came to the United States to go to graduate school in the Department of Planetary Sciences at Washington University in St. Louis. At the time, I was again one of the few women in my department. It was actually my Ph.D. adviser, who also happened to be a woman, who got me started down the path of studying meteorites. She asked me if I wanted to study these meteorites that are thought to come from the planet Mars. I remember seeing these Mars rocks and thinking to myself “wow, these rocks really look familiar to me like these lava rocks that we find on Earth and they formed on a completely different planet. I was totally hooked. What these rocks can actually tell us about past history of Mars, about whether there were ancient oceans on that planet, and whether the atmosphere was much thicker in the past. These are all questions that I wondered about. It turns out, these rocks can tell you all of this and a lot more.
So here’s the thing about meteorites: They are not some strange and obscure phenomenon. They are central to understanding the origin of our home planet to our very existence on this planet and even to our future! Many of you have probably already heard about the great extinction that happened 65 million years ago, when 70% of all species on our planet were wiped out by a large meteorite impact. And this is something that can happen to us in the future. But we can avoid that fate by gaining a better understanding of chemical and structural make up of meteorites and we can develop strategies for deflecting them.
What I really love about studying meteorites though is that the information that these objects tell us, basically help to answer some of humanity’s biggest questions: Are we alone in the Universe? Is there life elsewhere in our solar system or beyond? How do our planets form? How did Earth form? Why is it that our Earth is so different than other planets in our Solar System? How did life originate on our planet?
At the ASU Center for Meteorite Studies, my students and I focus on answering these big questions of course, but to initiate that process, we actually start by asking smaller questions, which are like the pieces of puzzle, which when we put them together, it can help us answer those bigger questions.
So here’s a couple of interesting things that we learned recently from the kinds of things we are working on in my laboratory: using dating techniques involving radioactive elements, we have entered the age of our Solar System as 4.568 billion years old and we know this age to within a few hundred thousand years. That’s like looking at a man 200 years old and being able to estimate his age to within half a month. Why is it even important to know the age of the Solar System to that precision? Well, this is the very basis, the very content for understanding the timeline of evolution of our entire Solar System and the planets. The other thing we have learned recently by studying the chemical makeup of meteorites like the one I just showed you, is that our Solar System began in very close proximity to a supernova, which may have triggered the very formation of the Solar System. And so the beginning of our Solar System were likely to be very energetic, very violent.
I am a geologist by training and so I look for ways to answer the big questions through the abundant rock record that we have here on Earth. In addition to telling us about our own planet, the rocks that we find on Earth also help us to understand the geological history of other planets like Mars. For example, my next project, which was just funded by NASA, will involve fieldwork in Iceland, where I will study rocks that are analogs to some type of rocks on Mars. By studying these rocks on Earth, I’ll actually be able to get to be a proxy geologist on Mars and I’ll get to understand how volcanism on Mars has effected the hydrosphere and atmosphere of the planet. Also, since the United States has now committed to sending human beings to the planet Mars in the 2030s, these types of studies like the project I am going to be doing in Iceland is going to help us to form strategies for human exploration by astronauts on the surface of Mars.
So through my research, I hope to I hope to continue to ask and answer questions that will give us insights into the workings of our planet and of our Solar System, and possibly also other planets, exoplanets as they are called, and other solar systems. However, the important thing to remember is that science is not about having all the answers. It’s about being able to ask better and more sophisticated questions. It is only by constantly pushing the boundaries of our knowledge that we can gain a deeper understanding of the complexities of our planet, our Solar System and even beyond our Solar System.
Science is also about the ability to ask and answer questions differently, from new perspectives and also from different approaches. One of the new approaches is working on a proposal to NASA to collect a sample from the surface of a comet. Why do we want to observe pieces of a comet though? Well, we have meteorites in our collection that have quite a lot of organic material and water in them, but they are invariably contaminated because they have been sitting on the Earth and they have been exchanging with the abundant water and organics in the environment. Now the sample we would bring back from a comet, would actually not be contaminated in this matter and so, preserve some of the most pristine organic materials in our Solar System. So by bringing back a sample to Earth and studying them in laboratories like the ones at ASU, we have the hope of understanding of how life may have originated on our planet.
If someone had told the 8-year-old me that I would grow up to be a geologist and would be able to do geology on other places, other planets in our Solar System like Mars and maybe even comets, I would have told them they were crazy. But by studying these rocks in laboratories here on Earth, in my own laboratory and by being able to study environments on Earth that are analogs to other places in our Solar System, other worlds in our Solar System, I am actually a planetary geologist in the broadest sense of the word.
I started this journey as an inquisitive young girl asking naive questions and the tools that I had back then were very simple too, just a magnifying glass to look at the fabric of rocks up close. The tools that I use now are much more sophisticated, but what really propels my research forward is still the questions. As kids, we were all innately and voraciously curious, but many of us seem to lose that spark of curiosity and wonder as we get older and maybe more cautious. So let’s be unafraid to ask those big, bold questions. Please do the young ones in your life a favor, both boys and girls in your life do them a favor, indulge their curiosities just like my mother did for me. Fuel their imagination by taking them to a museum or to science fairs. Let them know their dreams are not too farfetched-mine were not and theirs certainly are not.
Let’s always plan and looking up at the wonder of the night sky, the meteor showers, shooting stars, and keep asking those questions to propel us forward in our quest for knowledge and understanding of the world around us.