Science Adores a Vacuum

By Andrew Goldstein

Space is generally described as a void. It isn’t. Micrometeoroids smaller than the lead of a mechanical pencil speed through the cosmos. The sun constantly emits a solar wind of electrons, protons and alpha particles. Anything floating through our solar system is constantly barraged by both.

Earth’s atmosphere and magnetic field shield the planet, but airless bodies like asteroids and the moon are ever changing on some scale because of space weathering. Space weathering is a physical wear-and-tear these bodies go through when they’re hit by micrometeoroids and solar wind. This darkens their color and makes it difficult to see just what they are made of.

Scientists argue as to whether micrometeoroid bombardment or solar wind plays a more important role in the process of space weathering. To help answer that question, planetary scientists at Stony Brook University are planning to mimic the process of space weathering, using a small, specially built vacuum box and one of the brightest lights on Earth, an X-ray beam generated by a giant particle accelerator at Brookhaven National Laboratory.

“When we look at different bodies from Earth, we only see the information coming from the surface, but the surface has been processed a lot chemically. We want to study these processes in the laboratory.  We want to simulate that surface and energetic particle interaction in the laboratory,” said Mehmet Yesiltas, a Turkish postdoctoral researcher who was on a government fellowship in Stony Brook.

To do that, Yesiltas and his mentor, Timothy Glotch, an associate professor of geosciences, designed a cube that could keep samples in vacuum conditions while they are exposed to simulated versions of both solar wind and micrometeoroid bombardment. The cube can retain the vacuum while researchers analyze how the samples are affected.

They did this as part of  a program called RIS4E (or Remote In Situ and Synchrotron Studies for Science and Exploration) led by Glotch. One goal of the project is to work on getting accurate readings of the moon and asteroids using far away, or remote, sensing tools. Another goal is to develop tools and techniques to make the most of samples that may be brought back in future space exploration.

These vacuum cube experiments could show how solar winds and micrometeoroid bombardment affect airless bodies in space both individually and collectively. The cube would help refine remote sensing, so that future missions to airless bodies can know what different space rocks are made of and where to send astronauts to get the best samples.

The 8-inch steel vacuum cube Yesiltas designed has three thin, strong sapphire windows, with a movable stand inside on which to place rock samples. The cube is connected by a door to a smaller vacuum chamber where samples are inserted. While the samples face one window, researchers will shoot them with a laser calibrated to imitate the energy of one micrometeoroid. Then, they will move the sample to the second window to take a picture of it using high resolution X-ray imaging. They will see how the space weathering affects the way infrared (IR) analyzing tools see samples. The images can then be stacked, laser exposure after laser exposure, to make a high-quality video of changes that happen micrometeoroid by micrometeoroid.

“We can do one shot with the laser, and then take X-ray and IR spectra. Then we can take another shot with the laser and take an IR and X-ray spectra. And we can do a third shot – boom, boom, boom – ad infinitum until either the samples look like they’re stopping changing or we reach a point that we’re satisfied that we have enough information,” Glotch said.

To get the highest resolution, without letting any air leak into the vacuum and contaminate the samples, the window facing the X-ray camera could only be 4 millimeters thick. Taking their time to ensure the vacuum held, the engineers of MDC Vacuum delivered the tube months later than expected to the RIS4E lab.  

Creating this unique device took more time than anyone expected. After spending a year and a half designing the vacuum cube chamber, Yesiltas was called back to Turkey. The cube was still in its computer design phase.

“It hurt a little bit, coming back to Turkey without having done any experiments over there but that’s what I had to do,” Yesiltas said. “I was anxious to see the chamber and perform the first experiment with it, but I couldn’t because my fellowship required me to go back and I couldn’t extend my stay any more.”

Carey Legett, a geosciences graduate student, was asked to take over the vacuum cube project. At the time, Legett was working on computer modeling the effects of space weathering on lunar and airless body soils, the same effects Yesiltas and Glotch were trying to clarify.

“It dovetailed perfectly into what I was doing. There was an initial period where it was really hard because they had two years’ worth of work into this where they had all of these discussions about how things were going to work and decisions were made, and I come in with a completely outside view of how this project is working.”

While transitioning, Legett would spend hours discussing the design with Yesiltas and Glotch. He advised them to reroute the wiring and ground the device differently to keep the samples safer.

After receiving and inspecting the cube, the RIS4E team transported it to the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory. There, it will be run by Juergen Thieme, head of the Submicron Resolution X-ray (SRX) beamline. This is a full three years since the beginning of design.

NSLS-II accelerates electrons to 99.996 percent the speed of light, and uses their energy to create incredibly bright X-rays that create pictures of incredibly small samples. The SRX beamline has a resolution of 50 nanometers per pixel. If an iPhone 7 camera had that kind of resolution, each picture would only be able to show about four and a half red blood cells.

Starting in September, another post-doc is joining the team  specifically to work on the beamline with the vacuum cube project. According to Thieme, her addition to the team will help speed up the process to put the cube to use with the beamline. RIS4E should start getting results by the end of the year.

Space Weathering: FAQ

Space weathering shows in the gleaming edge of this meteorite  fragment at the American Museum of Natural History.

What is space weathering?

Space weathering is the set of processes that alter the surface of the moon and other planetary bodies that are not shielded by an atmosphere. Space weathering makes these bodies look darker and redder than they normally would be in the visible and infrared colors. Scientists generally think it is caused by some combination of solar wind and micrometeoroid bombardment, according to Kate Burgess, who researches the effects of space weathering at the Naval Research Laboratory in Washington DC.

What is solar wind?

Solar wind is a torrent of high-energy particles that the sun constantly ejects from its surface. These particles can range from (mostly) electrons, protons and helium to (rarely) elements as heavy as iron. It also ranges in energy but in general is considered “high energy.”

What is micrometeoroid bombardment?

Small pieces of rock or metal that range from the size of a human sperm cell to the size of a pinhead are floating through the cosmos. When one of them hits the surface of the moon or an asteroid, the heat and energy they deposit vaporizes some of that surface. As the vapor condenses back on the sample, it creates a glassy rim. The particles from solar wind do the same thing at a lower energy but more constantly.

Why should I care?

Space weathering affects all of our remote sensing measurements, like the ones we get from telescopes, and the ways we figure out what the moon and other bodies, like asteroids, are made of. Space weathering will have huge effects on any type of space exploration that we do, including sending humans out past the edges of the protective atmosphere of Earth. For example, the high-energy particles, without the atmosphere and magnetic field protection on Earth, are the kinds of things that cause radiation damage.

Which plays a larger role, solar wind or micrometeorite bombardment?

When the Apollo samples were brought back from the moon in the early 1970s, scientists thought that the darkening and reddening was mainly related to the glass and micron-sized iron grains found within that glass. That material is very much related to impacts from micrometeoroid bombardment.

With more research studying the samples in detail, they noticed iron particles one thousand times smaller than the previous grains. These are more related to the constant, lower energy deposits of solar wind.

They tried to differentiate: Is it the larger iron grains or the smaller iron particles that are creating the differences? Burgess said that a growing number of scientists are agreeing that the smaller particles darken and redden the samples more. There is still some argument about whether solar wind particles or by micrometeoroid bombardment is the more major player in lunar space weathering.

How can you tell which one is causing the weathering?

According to Burgess, the best way to figure out whether solar wind or micrometeoroid bombardment is the major player in space weathering would be to simulate each and then do detailed analysis using high-resolution imaging and spectroscopy on those samples. The imaging will let scientists visually compare the constructed and the natural samples. The spectroscopy uses lasers to determine the makeup of the samples, which can also be compared to natural samples. In this way, scientists can find which simulation technique matches most closely to the naturally space weathered samples.

The vacuum chamber that RIS4E developed is going to simulate space conditions for constructed samples. While in vacuum, the samples will get zapped by lasers to imitate either solar wind or micrometeoroid bombardment. The researchers hope they will be able to accurately simulate space weathering.

Mehmet Yesiltas

 

Carey Legett

Science Adores a Vacuum

By Andrew Goldstein

Space is generally described as a void. It isn’t. Micrometeoroids smaller than the lead of a mechanical pencil speed through the cosmos. The sun constantly emits a solar wind of electrons, protons and alpha particles. Anything floating through our solar system is constantly barraged by both.

Earth’s atmosphere and magnetic field shield the planet, but airless bodies like asteroids and the moon are ever changing on some scale because of space weathering. Space weathering is a physical wear-and-tear these bodies go through when they’re hit by micrometeoroids and solar wind. This darkens their color and makes it difficult to see just what they are made of.

Scientists argue as to whether micrometeoroid bombardment or solar wind plays a more important role in the process of space weathering. To help answer that question, planetary scientists at Stony Brook University are planning to mimic the process of space weathering, using a small, specially built vacuum box and one of the brightest lights on Earth, an X-ray beam generated by a giant particle accelerator at Brookhaven National Laboratory.

“When we look at different bodies from Earth, we only see the information coming from the surface, but the surface has been processed a lot chemically. We want to study these processes in the laboratory.  We want to simulate that surface and energetic particle interaction in the laboratory,” said Mehmet Yesiltas, a Turkish postdoctoral researcher who was on a government fellowship in Stony Brook.

To do that, Yesiltas and his mentor, Timothy Glotch, an associate professor of geosciences, designed a cube that could keep samples in vacuum conditions while they are exposed to simulated versions of both solar wind and micrometeoroid bombardment. The cube can retain the vacuum while researchers analyze how the samples are affected.

They did this as part of  a program called RIS4E (or Remote In Situ and Synchrotron Studies for Science and Exploration) led by Glotch. One goal of the project is to work on getting accurate readings of the moon and asteroids using far away, or remote, sensing tools. Another goal is to develop tools and techniques to make the most of samples that may be brought back in future space exploration.

These vacuum cube experiments could show how solar winds and micrometeoroid bombardment affect airless bodies in space both individually and collectively. The cube would help refine remote sensing, so that future missions to airless bodies can know what different space rocks are made of and where to send astronauts to get the best samples.

The 8-inch steel vacuum cube Yesiltas designed has three thin, strong sapphire windows, with a movable stand inside on which to place rock samples. The cube is connected by a door to a smaller vacuum chamber where samples are inserted. While the samples face one window, researchers will shoot them with a laser calibrated to imitate the energy of one micrometeoroid. Then, they will move the sample to the second window to take a picture of it using high resolution X-ray imaging. They will see how the space weathering affects the way infrared (IR) analyzing tools see samples. The images can then be stacked, laser exposure after laser exposure, to make a high-quality video of changes that happen micrometeoroid by micrometeoroid.

“We can do one shot with the laser, and then take X-ray and IR spectra. Then we can take another shot with the laser and take an IR and X-ray spectra. And we can do a third shot – boom, boom, boom – ad infinitum until either the samples look like they’re stopping changing or we reach a point that we’re satisfied that we have enough information,” Glotch said.

To get the highest resolution, without letting any air leak into the vacuum and contaminate the samples, the window facing the X-ray camera could only be 4 millimeters thick. Taking their time to ensure the vacuum held, the engineers of MDC Vacuum delivered the tube months later than expected to the RIS4E lab.  

Creating this unique device took more time than anyone expected. After spending a year and a half designing the vacuum cube chamber, Yesiltas was called back to Turkey. The cube was still in its computer design phase.

“It hurt a little bit, coming back to Turkey without having done any experiments over there but that’s what I had to do,” Yesiltas said. “I was anxious to see the chamber and perform the first experiment with it, but I couldn’t because my fellowship required me to go back and I couldn’t extend my stay any more.”

Carey Legett, a geosciences graduate student, was asked to take over the vacuum cube project. At the time, Legett was working on computer modeling the effects of space weathering on lunar and airless body soils, the same effects Yesiltas and Glotch were trying to clarify.

“It dovetailed perfectly into what I was doing. There was an initial period where it was really hard because they had two years’ worth of work into this where they had all of these discussions about how things were going to work and decisions were made, and I come in with a completely outside view of how this project is working.”

While transitioning, Legett would spend hours discussing the design with Yesiltas and Glotch. He advised them to reroute the wiring and ground the device differently to keep the samples safer.

After receiving and inspecting the cube, the RIS4E team transported it to the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory. There, it will be run by Juergen Thieme, head of the Submicron Resolution X-ray (SRX) beamline. This is a full three years since the beginning of design.

NSLS-II accelerates electrons to 99.996 percent the speed of light, and uses their energy to create incredibly bright X-rays that create pictures of incredibly small samples. The SRX beamline has a resolution of 50 nanometers per pixel. If an iPhone 7 camera had that kind of resolution, each picture would only be able to show about four and a half red blood cells.

Starting in September, another post-doc is joining the team  specifically to work on the beamline with the vacuum cube project. According to Thieme, her addition to the team will help speed up the process to put the cube to use with the beamline. RIS4E should start getting results by the end of the year.

Mehmet Yesiltas

 

Carey Legett

Space Weathering: FAQ

Space weathering shows in the gleaming edge of this meteorite  fragment at the American Museum of Natural History.

What is space weathering?

Space weathering is the set of processes that alter the surface of the moon and other planetary bodies that are not shielded by an atmosphere. Space weathering makes these bodies look darker and redder than they normally would be in the visible and infrared colors. Scientists generally think it is caused by some combination of solar wind and micrometeoroid bombardment, according to Kate Burgess, who researches the effects of space weathering at the Naval Research Laboratory in Washington DC.

What is solar wind?

Solar wind is a torrent of high-energy particles that the sun constantly ejects from its surface. These particles can range from (mostly) electrons, protons and helium to (rarely) elements as heavy as iron. It also ranges in energy but in general is considered “high energy.”

What is micrometeoroid bombardment?

Small pieces of rock or metal that range from the size of a human sperm cell to the size of a pinhead are floating through the cosmos. When one of them hits the surface of the moon or an asteroid, the heat and energy they deposit vaporizes some of that surface. As the vapor condenses back on the sample, it creates a glassy rim. The particles from solar wind do the same thing at a lower energy but more constantly.

Why should I care?

Space weathering affects all of our remote sensing measurements, like the ones we get from telescopes, and the ways we figure out what the moon and other bodies, like asteroids, are made of. Space weathering will have huge effects on any type of space exploration that we do, including sending humans out past the edges of the protective atmosphere of Earth. For example, the high-energy particles, without the atmosphere and magnetic field protection on Earth, are the kinds of things that cause radiation damage.

Which plays a larger role, solar wind or micrometeorite bombardment?

When the Apollo samples were brought back from the moon in the early 1970s, scientists thought that the darkening and reddening was mainly related to the glass and micron-sized iron grains found within that glass. That material is very much related to impacts from micrometeoroid bombardment.

With more research studying the samples in detail, they noticed iron particles one thousand times smaller than the previous grains. These are more related to the constant, lower energy deposits of solar wind.

They tried to differentiate: Is it the larger iron grains or the smaller iron particles that are creating the differences? Burgess said that a growing number of scientists are agreeing that the smaller particles darken and redden the samples more. There is still some argument about whether solar wind particles or by micrometeoroid bombardment is the more major player in lunar space weathering.

How can you tell which one is causing the weathering?

According to Burgess, the best way to figure out whether solar wind or micrometeoroid bombardment is the major player in space weathering would be to simulate each and then do detailed analysis using high-resolution imaging and spectroscopy on those samples. The imaging will let scientists visually compare the constructed and the natural samples. The spectroscopy uses lasers to determine the makeup of the samples, which can also be compared to natural samples. In this way, scientists can find which simulation technique matches most closely to the naturally space weathered samples.

The vacuum chamber that RIS4E developed is going to simulate space conditions for constructed samples. While in vacuum, the samples will get zapped by lasers to imitate either solar wind or micrometeoroid bombardment. The researchers hope they will be able to accurately simulate space weathering.