Meenakshi Wadhwa: Hello, my name Meenakshi Wadhwa. I’m 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 kinda dark. And to me it feels quite solid, feels heavy. But there’s nothing really particularly remarkable about this rock and its appearance.
But here’s the thing. If this rock could only tell you where it’s been, and all the places that it’s seen, all the things that it’s witnessed, it could be the most extraordinary tale 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 the Earth, they didn’t exist. All that there was in place of the solar system was a massive swirling cloud of gas and dust, at the center which was a newly born star, the sun.
As this massive gaseous disc cooled, and the very first solids began to condense out from that, they got quickly swept up into rocks that looked kind of like this one right here. And so as these rocks formed, they swept together to form larger and larger bodies, and eventually formed planets like the Earth.
But this rock that I’m holding right here, it escaped that fate. So literally it’s a remnant, a leftover fragment from the earliest stage of planet-building. It’s 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, and some come from Mars. They have traveled billions of miles through interplanetary space, until they finally fall on the 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 was a really inquisitive kid and asked lots of questions. I was about eight 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. And 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 I asked my mother, “Are we gonna run out of oxygen? Is the world coming to an end?” And she just laughed and she 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 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 Panjab 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, like becoming a nurse or a teacher. But my parents told me that I could do anything, that I could be anything. And while they were very very supportive of me, I was actually afraid to tell them what I really dreamed of being. And 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 Earth and Planetary Sciences at Washington University in St. Louis. And at the time I was again one of very few women in my department. It was actually my PhD advisor, 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 you know, these rocks really look sort of familiar to me, like these lava rocks that we find on the Earth. And they formed on a completely different planet. I was totally hooked.
What these rocks actually can tell us about past history on 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. And turns out that these rocks can actually tell you all of this and a lot more.
So here’s the thing about meteorites. They’re not some strange or obscure phenomena. 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 could happen to us in the future. But we can avoid that fate by gaining a better understanding of the chemical and structural makeup of meteorites. And we can develop strategies for deflecting them that way.
What I really love about studying meteorites, though, is that the information that these objects tell us basically help us 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 did our planets form? How did the Earth form? And why is it that our Earth is so different from 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 answering smaller questions which are like the pieces of a puzzle which when we put them together can help us answer those bigger questions.
So here’s a couple of interesting things that we’ve learned recently from the kinds of things that we’re working on in my laboratory. Using dating techniques involving radioactive elements, we have measured the age of our solar system to be 4.568 billion years old. And we know this age to within a few hundred thousand years. That’s like looking at a man who’s a hundred years old and being able to estimate his age to within half a month. Why is it even important to know the age of our solar system to that precision? Well, this is the very basis, the very context, for understanding the timeline of evolution of our entire solar system and the planets.
The other thing that we’ve learned recently by studying the chemical makeup of meteorites like the one that 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 our solar system. And so the beginnings of our solar system were likely to be very energetic, very violent.
I’m 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 can also help us to understand the geologic history of other planets like Mars. For example my next project, which was just funded by NASA, will involve fieldwork in Iceland, where I’ll study rocks that are analogues to some types of rocks on Mars. So by studying these rocks on the Earth I will actually get to be a proxy geologist on Mars, and I’ll get to understand how vulcanism on Mars has affected the hydrosphere and the atmosphere of the planet Mars.
Also, since the United States are now committed to sending human beings to the planet Mars in the 2030s, these types of studies, like the project that I’m going to be doing in Iceland, is going to help us to inform strategies for human exploration by astronauts on the surface of Mars. So through my research I hope to continue to ask and to answer questions that give us insights into the workings of our planet and our solar system, and possibly also other planets—exoplanets, as they’re called—in 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’s only by constantly pushing the boundaries of our knowledge that we can gain a deeper understanding of the complexities of our planet and of our solar system and even beyond our solar system.
So science is also about the ability to ask and answer questions differently. From new perspectives. And also from different approaches. And so 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 examine pieces of a comet, though? Well, we have meteorites in our collections that have quite a lot of organic material and water in them, but they’re invariably contaminated because they’ve been sitting on the Earth and they’ve been exchanging with the abundant water and organics in our environment. Now, the sample that we would bring back from a comet would actually not be contaminated in this manner, and so it would 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 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, on other planets in our solar system like Mars and maybe even comets, I would’ve 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 the Earth that are analogues for other places in our solar system, other worlds in our solar system, I’m actually a planetary geologist in the broadest sense of the word.
I started this journey as an inquisitive young girl asking naïve 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, of course, are much more sophisticated. But what really propels my research forward is still the questions.
As kids we are 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, and please do the young ones in your life a favor—both boys and girls in your life. Do them a favor and indulge their curiosity just like my mother did for me. Fuel their imagination by taking them to a museum, or to science fairs. Let them know that their dreams are not far-fetched. Mine were not, and theirs certainly are not. So let’s always plan on looking up in wonder at the night sky, at the meteor showers, at shooting stars, and keep asking those questions to propel us forward in our quest for knowledge and understanding of the world around us. Thank you.