The Stardust mission was one of the most unique projects that NASA and the research scientists developed. The purpose was to create a spacecraft that could navigate close to a comet and collect the extraterrestrial material that it gave off as it orbited nearby. There had never been an attempt of this type made and it involved finding a comet that was close to orbiting Earth, having a substance that could collect the material without damaging or contaminating it, and returning the collection to Earth safely.
Stardust also had a secondary job of collecting additional particles as the spacecraft speeded through space and both collections had to not only be kept separate, but had to be completely pristine to avoid contamination.
Launched in 1999, Stardust needed to carefully coordinate with an incoming comet. In 2004, the Stardust spacecraft made a flyby to the comet Wild-2 as it was getting near Earth. Stardust made a successful collection of the sample and two years later Stardust sent a capsule to a drop off in the Utah desert in 2006. Wild-2 id pronounced “vilt 2” and is named after Paul Wild, the discoverer of the comet.
The substance that was used for the collection was called “aerogel” and it is a lighter weight almost transparent material that has a lot of strength. Stardust had to remain behind the comet as the material was shed and particles became embedded in the aerogel. The requirement of a comet this close to the sun was needed as comets begin to eject material as they warm up.
Scientists wanted to study the samples to see if objects that were formed in the outer regions of the solar system were created differently than our planet.
Once the mission was over the spacecraft was still operational and was then recycled for the Stardust-NExT mission, which flew by comet Tempel 1 on February, 2011.
Scientists designed the NASA Stardust mission for the sole purpose of collecting uncontaminated samples of interstellar dust from a comet. This required perfect timing involving a voyage through space and coordinating with a comet that was close enough to the Earth yet also close enough to the sun to warm the comet.
Launched in 1999, Stardust went by an asteroid and then coordinated the close proximity with Comet Wild-2.
The mission was a success and NASA approved an extended mission to visit Comet Tempel 1 in 2011. Stardust then became the first spacecraft to visit two comets. During its almost 12 year travels to both comets Stardust traveled almost 4.7 billion mi/9.1 billion km.
The mission was closed, however, scientists are still reviewing the materials that were embedded in the aerogel and will probably be researching them for decades to come.
Stardust is shaped like a box and carries two solar arrays as well as a 101 lb/46 kg sample-return capsule that would carry the comet particle samples and was designed for a drop off into Earth’s atmosphere.
The spacecraft had two dedicated science instruments and several engineering instruments dedicated to the operation of the spacecraft and to collecting scientific data.
Although the technology on Stardust is very sophisticated, they assigned names that might sound more like they were from a space science fiction story.
Aerogel dust collectors: these are to collectors that are shaped like a tennis racket and have the ability of both extending from and extracting back into the spacecraft. The collectors are covered in aerogel and help to assure that the dust particles are pristine as the craft slows from the higher speeds to an all-out stop. One collector side gathers the material from the comet and the other side took samples of material that it encounters as Stardust makes its space travel.
The CIDA (Cometary and Interstellar Dust Analyzer): this technology determines the composition of the individual grains of dust as they collide with the silver impact plate.
The Navigation Camera was designed to get high-resolution images of the targeted comet.
Dust Flux Monitors monitored the flux and size distribution of the particles in the environment around Stardust.
The Aerogel Capturing:
The aerogel is the single most glamorous part of the Stardust mission. It’s actually a product of a silicon-based solid with sponge-like porous structures. When you look at it you almost think that it’s a cloud because it is mostly made up of empty space. It’s important for the particles be aimed to the collection area on Stardust and
this could get a bit tricky since the particles are traveling at up to 6 times the speed of a rifle bullet. Collecting in a convention method would harm the shape and possibly the chemical composition of the particles so the scientists had to come up with a material that would “catch and stop” without causing harm to the particles. When high-speed particles come in contact with the aerogel they are caught with very minimal chemical alteration or heating.
One of the scientists said that capturing the particles in aerogel was like collecting BBs when you shoot them into Styrofoam.
Upon capture, each of the particles creates a carrot-shaped track in the aerogel that is up to two hundred times the length of the particle. This track lets scientists trace the path of the particle through most of the transparent aerogel.
Finding a comet that was in the perfect orbit and rotation was a priority. Comet Wild-2, like most comets, was a leftover of the original formation of the planets and spent a majority of its life orbiting between Uranus and Jupiter. It had a close brush in 1974 with Jupiter that moved its orbit closer to the sun. The scientists scheduled Stardust to visit the comet and by that time Wild-2 had made only five close encounters with the sun. This is important because it also meant that much of its original shape, size, and material from 4.5 billion years ago was still intact.
The Surprise Discoveries:
It wasn’t until the capsule was dropped back to Earth that scientists could begin studying both the content of the material given off by Comet Wild-2 and the other materials that surrounded Stardust.
Examination of the materials is a slow process but the scientists almost immediately found a new class of organics that had been captured by the dust particles. These organics were more primitive than those that are found with meteorites.
Scientists also discovered calcium-aluminum-rich inclusions (CAIs), which are irregular particles that are some of the oldest materials in the solar system. They are made up of exotic compounds that are created at extremely high temperatures.
The first ever interstellar particles were part of the collection process. These are random particles that are drifting in the solar system in the area between the stars. Researchers believe that they probably formed before the sun was made. Locating them involved going through millions of interstellar images of the captured material. This is such a tedious and time consuming job that Citizen scientists are assisting to hunt for the particles by searching through the images.
The lead investigator of the Stardust mission released a statement indicating that Stardust confirmed that the particles from comets are indeed part of the solar system’s ancient building blocks. However, they were surprised at both the origin and nature of the particles.
Scientists originally thought that the particles would be mainly dust that formed around older stars in cold conditions at the edge of the solar system, beyond Neptune.
What the scientists found was that the particles were actually formed inside our solar system at very high temperatures. The comet’s rocky material had formed under white-hot conditions. Comets are made up of both ice and rocky materials and this discovery created a situation where they realized that comets are both “fire and ice.”
The particles that Stardust collected contain pre-solar “stardust” grains that were identified based on their unusual composition. It needs to be stated that these grains are considered to be very very rare.
The surprise for scientists was that there were both CAIs and chondrules, the rounded material from older areas of the solar system, in the same comet. This information was presented just three months after Stardust had delivered the particles at the annual Lunar and Planetary Science Conference. It was attended by 600 scientists and they were absolutely astounded at the information. The scientific implications are that matter that in great quantities in the inner solar system was somehow transported to the edge of our young solar system where the comets were created. Scientists had always assumed that the particles would be a majority of those that were formed around other stars and instead this shows that comets were really formed closer to the sun.
Other scientific surprises included information about the escaping dust with the expectation that it would increase and then with time, decrease. Instead, the rate of impact changes in spurts, kind of like dirt clods as they drift away.
The most astounding surprise was in the appearance of the comet. It was assumed it would be a dull object, but when the camera took images of it the comet turned out to be around a kilometer in size and had deep holes that were surrounded with vertical and even overhanging cliffs, spiky pinnacles hundreds of meters tall, and flat-topped hills with cliffs.
- Stardust was the first U.S. mission to obtain samples robotically in space and return them safely to Earth.
- Stardust was the first NASA mission dedicated to the exploration of a comet.
- Reviewing the samples sent back from Stardust, scientists have confirmed that comets are materials leftover from the early formation of the sun and the planets 4.5 billion years ago.
- Comets can contain and carry many of the organic materials that are thought to be part of the origins of life.
- When the early solar system was forming, comets repeatedly bombarded the planets.
- Comet Wild-2 almost collided with Jupiter in 1974.
- The coma is the dust and gas cloud that is given off by the nucleus of a comet. It takes several hours to fly through a comet’s coma.
- A majority of the comet’s particle that are leaving the comet have a diameter smaller than a human hair.
- Stardust collected less than one-thousandth of an ounce of dust from the comet.
- Over 1,000 of these particles would be large enough for complete scientific analysis, and millions of smaller particles are required to be analyzed as groups.
- Scientists are using some of the most powerful scientific instruments on Earth to study the cometary material.
- Stardust circled back by Earth to use a gravitational slingshot effect to head out to the comet. This meant that they could use a smaller rocket and it saved over eight million dollars.
- Stardust had a long way to travel to meet up with Comet Wild-2. It traveled 2 billion miles to the comet and then another one billion miles to return to Earth.
- Stardust was in space for seven years and had an average speed of 48,000 mph/78,000 kph.
- The return capsule from Stardust carrying the sample cargo used a parachute to land in Utah.
- The study of the particles sent back from Stardust has participation from the international scientific community.
- As Stardust flew by the comet, the Deep Space Network on Earth, which is a giant 20-story tall antenna, received transmissions of data and images from Stardust.
- The total distance traveled by Stardust would be compared to going beyond Mars and then over half of the distance to Jupiter.
- Stardust had to travel beyond the area in space where a good amount of sunlight was available. When it was at its farthest point, the onboard solar arrays had to generate enough electricity for the entire craft.
- When the capsule from the Stardust was dropped it hit the atmosphere of the Earth at 28,000 mph. This was faster than the Apollo mission capsules.
- The Stardust Outreach Program includes educational and public programs: the Virginia Space Grant Consortium, Space Explorers, Inc. and the JPL Ambassadors Program.