When I was 8 years old, the science teacher in my school taught us that we breathe in oxygen and let out carbon dioxide. I sat there thinking: “There must be all this carbon dioxide building up in the atmosphere. Are we going to be out of oxygen pretty soon?” I got really worried about it and ran home to my mother. “Did you know this?” I asked. “Is the world coming to an end?” My mother laughed and explained the cycles in nature that keep Earth systems in balance. So I learned at a young age that we don’t understand how much we don’t understand.

My father was a logistics officer in the Indian Air Force, and we moved every two years or so. At one point we lived in the south of the country in a house surrounded by mango groves. I’d climb the trees and pick the fruits—even before they were ripe. I just loved to bite into them. But the juice of raw mangoes can be pretty nasty. It’s corrosive and causes sores wherever it touches the skin. My mom would always say: “Don’t be impatient! Wait until those mangoes ripen!” The next day, the rash would show up on my face.

I learned a big lesson about patience when my mother died. I was 15 at the time, the oldest daughter, and I had to step into a motherly role with my younger sister. I also felt I had to take care of my dad. It was a big responsibility, and I had to learn to deal with the world from a completely different perspective. I realized I couldn’t always get things my way. I had to take other people into consideration.

You know, a lot of science is not exciting stuff. It’s a day-to-day thing that you have to do methodically and carefully until you get to the end product. My mother’s death made me look at the big picture—not the here and now. That was important to me down the road because impatience is just not how science works.

In India you pretty much have to decide out of high school what track you’re going to take. At age 17, you have to choose whether you’re going to be a doctor or an engineer or go for a liberal arts degree. That’s good if you know what you want to do. But if you don’t, you are forced into a discipline, and you have to follow that course. And if you flunk out, you might not get a second chance because there are age limits for admissions. It’s a one-shot deal.

I had always been interested in the sciences, but at that time I had just read The Fountainhead by Ayn Rand. The book inspired in me a glorified image of an architect. That image was not based on reality, but I was in love with it, which is part of the danger implicit in having to make such a big decision at 17. I wanted to be an architect, and I shut out everything else from my radar screen.

I applied to architecture school and did not get admitted. What now? There are certain jobs—doctor, teacher, nurse—that are considered acceptable for a woman in India, jobs that allow her to raise a family at the same time. I started to look at options, but all I really had to do was open the door.

At that time, we were living in Chandigarh, in the foothills of the Himalayas. Just looking at these mountain ranges is inspirational. It makes you feel that there are forces that are much bigger than we human beings. It makes you want to understand them.

I started to think about majoring in geology. “What’s that?” some people asked. I’m serious. But I went to visit the geology department of nearby Panjab University. There weren’t many women. At the time, it seemed like a haven for guys who couldn’t get into engineering or physics or whatever it was that they really wanted to do. So they were all looking at me, wondering, “What kind of loser are you?” For a little while I wondered if I should try to enroll in something that would be more acceptable in my social environment, but I’m glad I followed my instincts. I just wanted to better understand the world in which I lived. I guess it all goes back to oxygen and carbon dioxide.

Let’s say the length of your arms stretched out is the history of Earth. Then you take a nail file and rub your furthest fingernail. You’ve just removed all of human history. That’s one of writer John McPhee’s analogies for geologic time that I use when I’m teaching. But the truth is that the scale of geology is so much bigger than the human experience that it’s hard to wrap your mind around it. And at the time I was first introduced to it, there were distractions.

There was only one other girl in my class. I wasn’t dating anyone in particular and didn’t really want to. It soon became clear to me that it was considered weird to be a single woman who wanted to study rock formations, of all things. I felt like I was on the defensive at a time when I wanted to be open to all that I was learning.

It was stressful, so on geology field trips to the mountains around Chandigarh, I often went off on my own and sketched. The hardest part of sketching mountains, especially the Himalayas, is getting a sense of scale. You can put on paper only little vistas of what you see here and there. And what you see from one vantage point changes completely when you go to another.

That was a good thing to grasp. So I thought: “I should go to graduate school in the United States. The ratio of women to men there has got to be better.” Sure enough, I arrive at Washington University in St. Louis, and I’m the only woman in my class.

There I was, in the fall of 1989, plopped down in the middle of this country, where there are no mountains. It was a bit of a shock, but it probably didn’t matter where I lived because I always seemed to be up for three nights in a row, studying to catch up. I hadn’t had access to the latest textbooks in India. There was so much I didn’t have a clue about. One day, a faculty member, Ghislaine Crozaz, asked me, “Would you like to see a piece of Mars?”

It may be hard for you to imagine what it was like for me to hear those words at that time. I was 21. I knew about the manned Apollo 11 moon landing in 1969, but I didn’t know how many there had been after that, or that hundreds of kilograms of moon rocks were available to be studied. So my reaction was, “Whoa! You actually have a piece of Mars?”

She explained that some large impacts had most likely occurred there and chucked pieces of Mars’s crust into space, and that they eventually fell to Earth. The first piece of Mars I saw was a very thin slice that we looked at under a microscope. Most scientists who study meteorites believe that this sample came from Mars because the gases trapped in it have the exact same composition as the Mars atmosphere—a very distinctive composition that was determined by the Viking spacecraft in 1976. The section must have been about 30 microns thick—a micron is one thousandth of a millimeter—and at that level the minerals are essentially transparent. When polarized light is passed through them, you can see brilliant colors—reds and greens and yellows and blues that are diagnostic of the different minerals.

It was beautiful, but it was strange because it wasn’t weird. In fact, it was a little disappointing because the sample looked so much like Earth rocks that I’d seen. Then I thought, “What can you learn about the history of this other planet that’s supposed to have evolved so differently from ours, yet was able to produce this rock that looks so familiar?”

From that moment on, there was no pulling me away.

Professor Crozaz was using state-of-the-art equipment to analyze the sample’s formation. Working with mass spectrometers, where you can apply physics and chemistry to try to understand rocks from Earth and other planets, brought together everything I wanted to do and to learn about.

Then Professor Crozaz mentioned that she was going to hunt for meteorites in Antarctica...

A couple of years later, in December 1992, I was on a snowmobile. Six of us had been dropped by plane on an ice field roughly 100 miles from McMurdo Base, the largest camp in Antarctica.

There are no more meteorites falling on Antarctica than anywhere else in the world. But it’s easier to spot a dark rock atop light-colored ice. There’s no vegetation, nothing to confuse you. So any rocks you see on the surface of these thick ice sheets in Antarctica have to come from space.

Also, there’s a unique conveyer belt–like mechanism that operates in Antarctica. These ice sheets move very slowly from the interior of the continent out toward the shoreline. They’ve been around for hundreds of thousands of years. During that time, meteorites have fallen on them, become embedded, and gotten carried along. The deep freeze within the ice sheets keeps the meteorites virtually pristine. Sometimes a moving ice sheet gets blocked by a mountain where high velocity winds ablate the surface, eventually exposing the meteorites. As soon as they come up, these meteorites do begin to get weathered and oxidized, but it’s much less severe than the weathering that occurs in meteorites found in hotter or wetter environments. So, in many cases, Antarctic meteorites are the better samples to study.

You might find hundreds of meteorites in a zone the size of a football field. What you do is map out the field, then space the members of your team 20 feet apart and systematically drive your snowmobiles up and down the field. When you find the first one, you holler, everybody speeds over, and you jump up and down. Then you find 10 others, and you get sort of used to it.

I was in Antarctica for more than two months of that continent’s summer. Your sense of time gets warped when there’s constant light: The days just slip by. But then the wind would start gusting, and it’d get down to –70 with the windchill, and we’d have to stay in our double-walled tents. Try that for 10 straight days and you’ll know time at the other extreme. My best advice for when time becomes interminable is: read.

Every two or three weeks we’d get a mail drop. I’d open a letter from India and think about boundaries. You know, Indian families can be pretty governing. Parents often make important life decisions for their children regarding career and marriage. I was very lucky that my family supported my decisions. Because they did, I was able to stand in places where only a handful of people have ever been. My boundaries were evolving—they still are. If there’s one thing you learn as a scientist, it’s never close your mind off to things that seem far-fetched.

I went to grad school in St. Louis, so I know about Mark McGwire. I work at the Field Museum in Chicago, so I know about Sammy Sosa. I’ve seen how the crowd reacts after home runs, especially record-breaking runs. I would never dive over anyone’s back to try to grab a home-run ball. But in the spring of 2003, I got an idea of what the scramble must feel like.

Around midnight on March 26, a meteorite shower pelted houses and streets in Park Forest, a suburb south of Chicago. This was the most densely populated urban area ever hit by a meteorite shower. People reported objects falling through their roofs, and police took a lot of the meteorites as evidence. I headed over to the police station as soon as I heard. They had 15 or 20 pieces all laid out on a table like suspects in a lineup: a rogues’ gallery of meteorites! Freshest stuff I’ve ever seen. To see and hold a meteorite that has been in space only a few hours ago is amazing. And these were chondrites, a class of meteorites that were formed early in the history of our solar system.

I started out thinking that $1 a gram would be a reasonable price to offer. But dealers and collectors descended upon Park Forest, and it became a feeding frenzy. Meteorites that break through windows and roofs are actually worth more on the dealer-collector market. There’s nothing more scientifically interesting about the house smashers than any other pieces of meteorite, but their value rises when there’s a good story attached. If they crash through your roof, you may have hit the jackpot.