What Samples Have We Brought Back From Outer Space?
Mankind has sent out numerous probes into our solar system. They act as extensions of us, going places and doing science that we cannot accomplish as of now. Most of the time, it is a one-way trip, with the spacecraft going to the object of study and never returning. Sometimes, however, we have a mission that requires the space probe to return, and frequently with a special payload. Besides the Apollo and Luna missions of the past, which brought back 842 pounds and 11.5 ounces of moon rocks (Kruglinski 13), here is but a selection of spacecraft that have returned something from space back to Earth.
The first US sample-return mission since the Apollo program. This probe was sent to collect solar wind and return it to Earth. Over a 27 month period, it orbited at the Earth Lagrange Point 1 (for quality and quantity, for that placed it between us and the sun) and gathered samples of these particles, which have elements and traces of what formed the solar system about 4.6 billion years ago. Hence, by analyzing the samples we might learn something about our own history. Around Genesis at L1 was a particle density of 10 atoms per cubic centimeter. The particles would become embedded in sapphire and diamond wafers as well as sheets of gold foil that were exposed on the spacecraft (Forte 14, Wadhura 54).
Unfortunately, the probe was not recovered as planned. It crashed into Utah on September 8, 2004, exposing the equipment to the elements. Many feared that the mission would be over, but researchers had a game plan ready to help salvage material. Led by principal investigator Donald Burnett, scientists used ultra-pure water and acid to remove contaminants and also enlisted the aid of lasers to pinpoint any solar particles while at the Astromaterials Acquisition and Curation Office at Johnson Space Center. It was also fortunate that the wafers themselves were mostly intact. Only 15% of the oxygen isotope measuring wafers were destroyed. This was extremely lucky because scientists wanted the data to help resolve why oxygen levels in different places of the solar system vary. In the end, about 1/1000000 of an ounce of solar wind was collected and several theories of our solar system formation were eliminated (Forte 14, Kruglinski 13, Wadhura 55).
One interesting result of Genesis involved neon isotopes and the moon! Apollo missions brought back soil samples which had an increasing amount of neon isotopes the deeper the sample was. Based on the levels of the isotope, which formed courtesy of the solar wind as well as larger solar particles, the sun should have had a higher level of activity in the past. To help explain this, scientists measured the neon levels from the probe after exposing the wafers to a nitric acid vapor, releasing the neon gas. Based on the wafers from Genesis, scientists found that the neon isotopes did not vary with depth but actually started right on the surface and went all the way through. It matched lunar levels to an extent but had two differences. One, the wafers have not had as much exposure to cosmic rays as the surface of the moon. Two, the probe collected neon isotopes not seen on the moon. Both suggest that space weathering may remove these isotopes and cause a gradual reduction of neon the closer to the surface you go. This means that the higher solar activity suspected of the past likely did not happen (Nevillis).
Another interesting finding was the most common elements encountered by Genesis: hydrogen, helium, oxygen, and nitrogen. Notably, amongst these elements a small but detectable difference in isotope levels was found when compared to Earth values and therefore hints at something hidden in the solar system's formation. Why? Because the Sun is 99% the mass of the solar system, therefore the planets should have much in common when it comes to element makeup (not that we should be a ball of plasma but that variations of elements like isotopes should be tightly correlated). However, the nitrogen isotopes were an exact match for Jupiter. Clearly, something different was going on with the terrestrial planets than we currently understand (Wadhura 56-7).
This spacecraft was going after a different kind of payload: asteroid dust. Launched May 9, 2003, it arrived at asteroid Itokawa a few years later and on November of 2005 it finally managed to land on the asteroid after the first attempt had to be aborted. It was not an easy feat considering that Itokawa only has about 1/100000 the gravity that Earth possesses. If Hayabusa were to make an extraction attempt by drilling it would most likely result in it pushing off the surface of the asteroid (McNicol 12).
So to ensure success a different approach was taken: an object was shot into the asteroid and Hayabusa was standing by to collect the flung-off material. Altogether, about 1/10 of an ounce was gathered and began its return trip to Earth, a 180 million mile trip, in early December. Naturally, a problem developed. The ion engine that propelled the spacecraft developed a leak and thus caused Hayabusa to miss an assist that would have shortened its return trip. Instead of a June 2006 arrival, it actually returned to Earth on June 13, 2010. There was a short delay between the return of the material and the announcement that the material was indeed form an asteroid because of potential contamination but scans from an electron scanning microscope confirmed their origination. Analysis of the collected material, which averaged in size at around 10 micrometers, has given scientists a better understanding of asteroid chemical makeup and also how they are related to one another (McNicol 12, Malik).
Launched on February 7, 1999, Stardust’s mission was to gather a sample of comet Wild 2. To ensure that the capsule would not be damaged during the sampling portion of the mission, scientists had the craft rotate to ensure even exposure and also had whipple shields (series of panels that are covered in Nextel) protecting the solar panels and the center of the probe from any pesky particles large enough to cause some damage (Watanabe). After traveling in space for years and covering 3.22 billion kilometers, Stardust intercepted the comet in 2004 and got within 230 kilometers of its surface (Watanabe "NASA"). In January of 2006, the 95-pound container of the samples separated from Stardust and landed on Earth. The container was built with an aerogel that would capture particles as they collided (Kruglinski 13). After dropping off its payload, Stardust was then redirected to investigate comet Tempel 1, which had previously been visited by the Deep Impact probe. After the flyby, Stardust was shut down in 2011.
When scientists looked at the tiny particles that were collected, they found that the data hinted at comets having formed closer to the sun than previously thought. Olivine, a green mineral made primarily of iron and magnesium, was one of the chemical clues that led scientists to this conclusion for it could have only formed in warm regions like those near the Sun (Watanabe "Stardust"). They also found trace amounts of glycine, an amino acid critical to the structure of DNA. At first scientists were not sure if the samples had been contaminated with Earth material. But fortunately, the carbon-13 levels within the sample did not match the levels seen in Earth-based glycine. Whether or not this is evidence of panspermia remains to be seen (Jenner).
So how much closer to the sun did they form? One particular dust speck, named Inti (or the Inca god of the sun) was a shocker to scientists. They were expecting dust from the comet to contain carbon and ice but instead got rock, tungsten, and titanium nitride. Those compounds only existed near the sun at a temperature of 3000 degrees Fahrenheit. Something caused material that was initially near the sun to be cast off to the far reaches of the solar system. Scientists best bet for this rests with the Nice Model (Irion 46).
And to top off those exciting findings was the announcement in 2014 that 7 possible particles of interstellar dust, from beyond out solar system, were detected. If true, they would be the first samples of their kind ever returned to space. But how did scientists reach this conclusion? One of the detectors on Stardust was pointed to the comet but the other was pointed away in the direction of the constellation Ophiuchus for 195 days. A long time. Long enough to reasonably be confident that they are not from the comet and instead from...out there. When the detector was returned to Earth, scientists found lots of possible particles but a majority was debris from the spacecraft. A few remained unexplained for based on chemical make-up, however. Additionally, some of the foil around the detector had pits in it with trace amounts of matter that are different from Stardust and hence also possible interstellar particle collisions (Choi).
Carbon, nitrogen, and oxygen were in the dust and are likely products of supernovas and old stars who have depleted their fuel into heavier elements. Some of them had sulfur while others had olivine. And they are small, about 3 picograms each (1 picogram is a trillionth of a gram). The larger ones seem to be fluffy and crystalline in structure, not necessarily fitting with models of stellar growth. Additionally, Stardust encountered less interstellar particles than expected based on its location, compared to previous results from Genesis and Ulysses. This could be because of solar pressure pushing the particles away (Choi, JPL).
Over these three missions, three different types of targets were visited. We went to an asteroid, collected solar particles, and also went by a comet. Through all of these sampling missions we have gained a deeper understanding of the solar system. Who knows what imaginative missions await us.
Choi, Charles Q. "NASA's Stardust Probe May Have Nabbed Dust From Interstellar Space." HuffingtonPost.com. Huffington Post., 14 Jun. 2014. Web. 04 Jan. 2015.
Forte, Jessa. “The Resurrection of Genesis.” Discover Dec. 2004: 14. Print. 09 Sept. 2014.
Irion, Robert. "It All Began in Chaos." National Geographic July 2013: 46. Print.
Jenner, Lynn. "NASA Researchers Make First Discovery of Life's Building Block in Comet." NASA. NASA. 17 Aug. 2009. Web. 04 Jan. 2015.
JPL. "Stardust Team Reports Discovery of First Potential Interstellar Space Particles." Astronomy.com. Kalmbach Publishing Co., 15 Aug. 2014. Web. 04 Jan. 2015.
Kruglinski, Susan. “Stardust Memories.” Discover April 2006: 13. Print. 09 Sept. 2014.
Malik, Tariq. "Asteroid Dust Successfully Returned by Japanese Space Probe." Space.com. Purch, 16 Nov. 2010. Web. 28 Oct. 2015.
McNicol, Tony. “Japan Stakes Its Claim in Space.” Discover Feb. 2006: 12. Print. 09 Sept. 2014.
Nevillis, Amiko. "Genesis Findings Solve Apollo Lunar Soil Mystery." NASA.gov. NASA, 20 Nov. 2006. Web. 23 Aug. 2015.
Wadhura, Meenakski. "Order from Chaos: Genesis Samples the Solar Wind." Astronomy Oct. 2013: 54-7. Print.
Watanabe, Susan. "NASA Spacecraft Makes Great Catch...Heads for Touchdown." NASA. NASA, 02 Jan. 2004. Web. 11 Dec. 2014.
---. "Stardust Samples Show Evidence of Fire, Ice" NASA.gov. Nasa, 13 Mar. 2006. Web. 04 Jan. 2015.
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© 2014 Leonard Kelley