Unusual meteorites may soon be found in the furnace of an Olin Hall laboratory, where second-year graduate student Holly Brown hopes to synthesize materials that could answer questions about the universe's oldest materials.
Brown's research is in petrology - the study of rocks. She deals with pallasites, rare meteorites that are not often found on Earth. Pallasites have a beautiful appearance due to their extraordinary properties and mysterious formation: They are essentially chunks of iron and nickel metal with a green mineral, olivine, running through them.
"Meteorites are kind of the origin of our solar system and everything is thought to have come condensed from them. It's how we have planets. So I'm interested in making a laboratory or synthetic analog to what we see in nature," she said.
Brown first fired up the oven a month ago, and over the past few weeks it has been getting progressively hotter, finally reaching the desired temperature of around 3,000 degrees Fahrenheit, which is six times hotter than that of a kitchen oven's maximum. Two weeks ago, Brown officially began the experiment.
"Pallasites [exist in] two main phases, as a metal [made of] iron and nickel - right now we're just focusing on the iron aspect, because it's mostly iron - and [as] a silicate mineral called olivine."
Brown's process to create this material consists of filling a capsule with about one teaspoon of iron powder, then encasing the capsule within several blocks of ceramic, which can withstand very high temperatures.
She drills a hole in the top ceramic block so that if the iron melts and moves around, it can flow upwards instead of sinking through the pores of the ceramic into the bottom of the oven.
Brown and the team helping her knew that the iron would sink due to its density, but there was a lot that could not be foreseen about these particular materials at this particular temperature for this much time.
For one thing, they had to hope that the iron wouldn't react with ceramic, and since the oven was so hot Brown could not check on the sample very often once it reached its top temperature, meaning hours of waiting and hoping that when she could finally remove the sample nothing would combust due to the sudden extreme heat leaving the furnace.
As with all beginning scientific experiments, unforeseen complications ensued. Brown's first experiment, as she put it, "exploded a little bit." The silicate capsule in which she had placed the iron powder melted. Although ceramic is able to withstand high temperatures, the time in which it was in the unimaginably hot oven proved too much for the blocks, which began to flow like liquid and looked "deformed like a marshmallow," according to Brown.
She laughed that security was called because of the weird smell emanating from the oven all week, and she recounted having a colleague stand by her at the oven with a fire extinguisher when it was time to remove the sample. The experiment certainly was not perfect, but Brown had not expected it to be and she knows where to go from here.
"I didn't realize that some material properties, their quoted temperatures are just for short amounts of time, whatever that may be, hours or a minute. So I need to be a little bit more careful with reading in the texts what something can withstand and think about the context of a prolonged heating period."
Brown said she will find new capsule materials that will not melt in these conditions so that in time she can contain the iron sample and add olivine so that an actual pallasite will be visible.
When asked why she thought all this trouble and all this work was worthwhile, Brown replied, "If we have similar compositions or similar numbers for real pallasites as we do in our experiment, then maybe we can start to piece together the formation history, because what we did in the lab is documented and it's for sure. What we know for formation in space is a theory."
Brown pointed out that physicists have theorized a lot about the universe and its formation, and chemists have been able to analyze falling meteorites and other materials that can give us hints, but for an igneous petrologist like Brown, the importance lies in the texture of the rocks she finds, as well as the ones she is creating.
"Anything that comes from an original composition [in space] can tell us maybe about how we evolved, or when we evolved. There's tons of implications for anything," Brown said. She cited the familiar example of Pluto's de-classification as a planet, though its status was once set in the minds of schoolchildren (and adults) everywhere.
Research like hers could lead to new systems of meteorite classification and new understandings of processes on Earth and elsewhere in the solar system.
Brown's adviser, Bruce Marsh, has been instrumental to this unique project. Marsh encouraged her to do an experiment with meteorites, and she decided to focus on pallasites. No one has ever done such experiments with these temperatures and these materials before.
"The University is great because we have a wide range of funding available to us and a lot of scholarships are available to graduate students in particular."
After graduating with a B.S. in Geophysics from the University of Rochester in 2006, Brown came to Hopkins a year ago to do a five-year Ph.D. program in the Earth and Planetary Sciences Department.
She said her first year was productive because she had time to come up with a dissertation project, which will comprise this pallasite research, and she was able to wait a year before having to teach. She is a teaching assistant for a course taught by Marsh.
Marsh has recently been profiled by National Geographic for a nature documentary series that will air this summer and will include a presentation on his work. Brown cited working with him as her primary reason for coming to Hopkins.
With Marsh and another colleague, Brown went to Antarctica over winter break to help collect samples and have an "educational experience."
She said that due to Antarctica's bare surroundings compared to the rest of Earth, she was able to do a lot of "in-your-face geology" there with no trees or weathering elements to obscure what she was looking for.
Brown expects to work on this project for several more months before she has a pallasite that she can work with. She is prepared to make as many mistakes as she needs to before she gets the sample right, and she hopes to explain previously unfathomable phenomena.
"It's very open to change until you actually get what you're looking for."
