The result is a realistic looking, true-size facsimile of a martian meteorite called "Block Island." NASA's Mars Exploration Rover Opportunity found it in 2009. Block Island is the largest meteorite yet found on Mars. It is an iron-nickle meteorite about the size of a small ice chest. The real Block Island probably weighs a half-ton. You could easily carry its plastic twin under an arm.
Most meteorites break up when hitting the ground because today's martian atmosphere is not dense enough to slow them down enough. Scientists say this meteorite could have landed on Mars intact only if it had two things: a very specific entry point into the atmosphere and a very shallow flight path. That would slow it down enough to keep it from breaking apart upon landing.
First 3D-printer model of a meteorite on another planet based on rover data
This 3D-printer model of a meteorite is the first of its kind, made from precise measurements by a rover on Mars. It potentially opens the door to other detailed models of objects and terrain on Mars or elsewhere in the solar system. Researchers expect the technology will also find uses in other applications on Earth, such as life-size 3D reproductions of remote objects or settings.
Scientists based the design of the plastic meteorite on detailed measurements and stereo images taken by Opportunity's panoramic camera, or PanCam. The rover took pictures during its 360-degree study of Block Island five years ago. Researcher Kris Capraro works at NASA's Jet Propulsion Laboratory in Pasadena, California. He says one reason the rock could not be replicated back in 2009 is that the rover could not see every square inch of the meteorite. The missing data created holes in the computer model. That made the rock data unfit for 3D printing (stereolithography). The first model Capraro tried to make had lots of holes, so it wouldn't hold together. It looked like a partially melted plastic pot scrubber.
Life-Size from Another Planet
Last summer, said Capraro, researchers solved the problem of filling in the missing data and built several small models of the meteorite. "Holding one of these small models in your hand was very cool," said Capraro, "but to experience the meteorite that lay before Opportunity, it had to be BIG -- an actual-size model of the meteorite." Creating a life-size model was the only "natural" way to visualize fully what Opportunity beamed home as a 2D image to humankind on Earth."
The researchers applied software methods usually used to help navigate the rover. They created depth meshes of the meteorite's surface from six positions, then combined them into a three-dimensional digital model, said Capraro.The 3D printer used for the project is a mainstream tool used in office and light industrial settings. It builds the model from a spool of ABS (acrylonitrile butadiene styrene), a common plastic about the diameter of weed-whacker cord. To build the contour of the object it is replicating, the printer slowly heats the plastic and layers it precisely.
Next Best Thing to Being There
"It's been an interesting challenge to create the large 3D model," said Capraro, who also creates navigation maps of the Martian surface for planning rover drive paths. The rock was much bigger than the 3D printer's building space, about the size of the inside of a kitchen oven. To solve that problem, researchers broke up the computer model of the meteorite into 11 sections. It took 305 hours and 36 minutes to print the parts: 281.11 cubic inches of acrylic thermoplastic media and 37.29 cubic inches of plastic support media that forms the support structure inside the rock model. Then, researchers were ready to assemble the parts. Then they finished by painting it to match the real rock's color based on rover images. For now, said Capraro, "it's the next best thing to bringing back real Martian rock samples back to Earth."