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- Mars (NASA missions, evidence of life on Mars?)
- Voyager
Mars (last updated February 8, 2004) (back to top)
Assuming no probelms, the two land rovers that NASA landed on the surface of Mars in January 2004 will spend three months each exploring their respective touchdown areas for signs that the environment once had water or once could have supported life. The Spirit rover landed on January 3 in Mars' Gusev Crater, and the Opportunity rover landed on Jan. 25 in the Meridiani Planum, on the opposite of the planet from Spirit.
These rovers are part of NASA's ongoing efforts to locate areas on Mars that may once have contained water and thus would be likely areas to find evidence of past life. They also mark NASA's second and third rovers on another planet, following the Sojourner land rover that spent three months on the surface of Mars beginning in July 1997.
Looking forward, NASA plans to send two more exploration rovers to Mars in June 2003 to conduct tests on two locations that might have once had water. As of October 2002, NASA's long-term plans included another reconnaissance satellite in 2005, a long-range mobile science lab in 2009, and the first-ever mission that would return samples to Earth in 2014 or later.
Life on Mars?
Mars exploration efforts were rejuvenated in the late 1990s by an arguably premature report that a meteorite containing carbonate particles did seem to show evidence for primitive life on Mars about 3.6 billion years ago.
The meteorite, identified as ALH84001, was found in 1984 in the Allen Hills region of Antarctica, and it was not identified as being from Mars until 1993. It weighed just 1.9 kilograms and was about the size of a potato, and it is one of just 12 meteorites that had been identified as of the late 1990s as coming from Mars. The meteorite is believed to have crystallized about 4.5 billion years ago on Mars and to have cracked sometime while there, to have been dislodged from Mars by a huge impact about 16 million years ago, and to have landed on Earth about 13,000 years ago.
In August 1996, NASA officials announced that a study of ALH84001 had concluded that it proved the existence of some kind of primitive life on Mars. Dave McKay and eight co-writers pointed to several features of the meteorite, such as the resemblance of small carbonate areas on the rock to microfossils and the presence of magnetite particles that could have resulted from biological reactions, and wrote that while "none of these observations is in itself conclusive for the existence of past life," they together amounted to "evidence for primitive life on Mars."
However, scientists have continued to study the meteorite and have not definitively confirmed McKay's initial conclusions as of yet. Several of the features that were identified as suggestive of life on Mars have been discredited, and some have argued that bacteria could not be small enough to leave behind microfossils.
As a team of writers put it in a November 2001 article, "data amassed since the McKay paper have resulted in the effective elimination of all but one of the original arguments. The case for former Martian life now rests on the identification of a small subset of the magnetite crystals in ALH84001 as biogenic in origin." A team of NASA scientists did conclude in a February 2001 article that the shape of the magnetite crystals found in ALH84001 provide evidence of past biological activity and concluded that the decomposed remains of bacteria could have been deposited in the cracks of ALH84001 while it was still on Mars, but others have criticized this conclusion.
Missions to Mars
Whether or not ALH84001 does show sufficient evidence of past life on Mars, the news helped rejuvenate NASA's efforts to reach the fourth planet. The first wave was in the 1970s and culminated with the Viking 1's first successful landing in 1976, and a second wave in the early 1990s failed when the Mars Observer lost contact just before entering Mars orbit in 1993. NASA launched a new era in 1996 and 1997 with the Pathfinder mission and the Mars Global Surveyor, and followed that up in 2001 with the Mars Odyssey 2001.
The Pathfinder landed on July 4, 1997 with the Sojourner land rover, the first rover on another planet; Sojourner provided the first close-up photographs of Mars in decades and lasted for three months. The Mars Global Surveyor reached Mars orbit in September 1997 and began mapping the planet in March 1999. The Mars Odyssey 2001 arrived at Mars in October 2001 and also mapped the planet for minerals and water.
Sources: NASA is on-line here. The original article by Dave McKay and eight co-authors concluding that ALH84001 showed evidence of past life on Mars is Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001 (on-line here. Pictures of ALH84001 are on-line via NASA here. Peter R. Buseck et al, Magnetite morphology and life on Mars, Proc. Natl. Acad. Sci. USA, Vol. 98, Issue 24, 13490-95 (November 20, 2001), on-line via the PNAS here. E. Imre Friedman et al, Chains of magnetite crystals in the meteorite ALH84001: Evidence of biological origin, Proc. Natl. Acad. Sci. USA, Vol. 98, Issue 5, 2176-2181 (February 27, 2001), also , on-line via the PNAS here. and with a NASA press release on-line here. NASA has collected information on its various missions to Mars on-line here. Malcolm Walter, The Search for Life on Mars (Perseus Books, 1999).
Voyager: Leaving the Solar System (last updated February 15, 2004) (back to top)
The twin Voyager 1 and 2 spacecraft were launched in 1977, passed the outer planets in the 1970s and 1980s, and are, as of late 2003, beginning to leave the solar system. On November 5, 2003, Voyager 1 reached 90 astronomical units (AU), or about 8.4 billion miles, from the Sun.
Voyager 1 may have passed through the termination shock, an area where the solar wind (a thin stream of electrically-charged gas blown from the Sun) slows dramatically in speed because of pressure from interstellar gases. Some scientists argued in 2003 that Voyager 1 had already crossed this area, but others have disagreed. The debate could be decided if Voyager 1 could measure the speed of the solar wind, but that equipment no longer functions.
In any event, once Voyager 1 passes through the termination shock, it will be in the heliosheath, a region where the Sun's influence wanes and the large changes in plasma flow direction and magnetic field orientation are expected to occur. Voyager 1 will then spend years crossing through the heliosheath and eventually will cross the heliopause, which marks the end of the Sun's magnetic field and the outward flow of its winds.
The following image was created by a NASA artist and depicts the Voyager spacecraft's expected journey.
Once Voyager 1 crosses the heliopause, it will truly be conducting interstellar exploration. The Voyagers have enough fuel to operate until 2020 but will continue to drift afterwards, possibly forever.
Sources: NASA has more information on Voyager here. A November 15, 2003 press release about Voyager's progress is on-line here and contained the graphic used above.
Voyager: The Golden Record (last updated February 15, 2004) (back to top)
The twin Voyager 1 and 2 spacecraft, which are now beginning to leave the solar system, each carry with them a golden record bearing images, sounds, and music which an alien civilization may use someday to get a better understanding of humanity.
What is on this record? In order, the record contains the following:
- 118 pictures, depicting such things as the solar system, the structure of DNA, human anatomy and development, Boston, the Taj Mahal, the United Nations, a page from the Isaac Newton's System of the World, a sunset, and the score of quarter and violin for the Cavatina from Beethoven's String Quarter No. 13;
- The first two bars of the Cavatina from Beethoven's String Quarter No. 13, as depicted in the picture preceding it in sequence;
- Greetings from President Jimmy Carter ("This is a present from a small distant world, a token of our sounds, our science, our images, our music, our thoughts and our feelings. We are attempting to survive our time so we may live into yours. We hope someday, having solved the problems we face, to join a community of galactic civilizations. This record represents our hope and our determination, and our good will in a vast and awesome universe.");
- A list of Congressmen involved with NASA operations;
- Greetings from United Nations Secretary General Kurt Waldheim;
- Greetings in 54 different languages;
- Greetings from members of the United Nations;
- Whale greetings;
- Sounds of the Earth, such as human footsteps and laughter, volcanoes, crickets, an infant's cries, and a message in Morse Code, "Ad astra per aspera" ("To the stars by hard ways," which is Kansas's state motto); and
- 27 pieces of music from around the world (detailed below).
Carl Sagan, who helped pick the contents of the record, wrote that it was important to send musical selections in order to tell something about how humans felt. "Our emotional life is more difficult to communicate [than humans' intellectual life], particularly to beings of a very different biological make-up. Music, it seemed to me, was at least a credible attempt to convey human emotions," he wrote.
The musical-selection process involved long debates and much consultation with experts. The two criteria were that a wide range of cultures should be included, and that every selection should "touch the heart as well as the mind," according to participant Timothy Ferris. Copyright issues also played a part. Sagan wrote that the Beatles' "Here Comes the Sun" would have been included but for some murkiness about the legal status of the piece; the Beatles gave their approval but did not own the copyright to the song.
Of the 27 pieces selected, seven are by Bach, Beethoven, Mozart and Stravinsky, 16 are native music from around the world (including a Navajo Indian night chant), one is a piece of Renaissance music, and three are pieces by 20th-century American musicians, all of whom are black.
- Bach, Brandenburg Concerto No. 2 in F, First Movement, performed by the Munich Bach Orchestra with Karl Richter, conductor.
- Java, court gamelan, "Kinds of Flowers."
- Senegal, percussion.
- Zaire, Pygmy girls' initiation song.
- Australia, Aborigine songs, "Morning Star" and "Devil Bird," recorded by Sandra LeBrun Holmes.
- Mexico, "El Cascabel," performed by Lorenzo Barcelata and the Mariachi Mexico.
- Chuck Berry, "Johnny B. Goode."
- New Guinea, men's house song.
- Japan, shakuhachi, "Cranes in the Nest," performed by Coro Yamaguchi.
- Bach, "Gavotte en rondeaux" from the Partita No. 3 in E major for violin, performed by Arthur Grumiaux.
- Mozart, The Magic Flute, Queen of the Night aria no. 14, performed by Edda Moser and the Bavarian State Opera with Wolfgang Saivallish, conductor.
- Georgian S.S.R., chorus, "Tchakrulo."
- Peru, panpipes and drum.
- Louis Armstrong and his Hot Seven, "Melancholy Blues."
- Azerbaijian S.S.R., bagpipes.
- Stravinsky, Rite of Spring, Sacrificial Dance, performed by the Columbia Symphony Orchestra with Igor Stravinsky, conductor.
- Bach, The Well-Tempered Clavier, Book 2, Prelude and Fugue in C, No. 1, performed by Glenn Gould on piano.
- Beethoven, Fifth Symphony, First Movement, performed by the Philharmonia Orchestra with Otto Klemperer, conductor.
- Bulgaria, "Izlel je Delyo Hagdutin," sung by Valya Balkanska.
- Navajo Indians, Night Chant.
- Holborne, Paueans, Galliards, Almains and Other Short Aeirs, "The Faerie Round," performed by David Munrow and the Early Music Consort of London.
- Solomon Islands, panpipes.
- Peru, wedding song.
- China, ch'in, "Flowing Streams," performed by Kuan P'ing-hu.
- India, raga, "Jaat Kahan Ho," sung by Surshri Kesar Bai Kerkar.
- Blind Willie Johnson, "Dark Was the Night."
- Beethoven, String Quarter No. 13 in B flat, Opus 130, Cavatina, performed by the Budapest String Quarter.
Of the three American musicians represented, Armstrong and Berry are probably familiar to most audiences. Blind Willie Johnson, whom Josh Lyman described in an episode of the West Wing, was a blues musician who was born around the beginning of the 20th century, was blinded by his stepmother at the age of 7, and was a master of slide guitar playing. Johnson died of pneumonia in 1947, after being turned away from a hospital that refused to treat him because he was blind.
His song, "Dark was the Night," was an old hymn that he recorded on December 3, 1927; its full title is "Dark was the Night and Cold Was the Ground on Which Our Lord was Laid." Timothy Ferris, who helped select the song for inclusion on Voyager's record, wrote that Johnson's recording is "one of the most fundamentally moving pieces of music ever recorded."
Sources: Carl Sagan et. al, Murmurs of Earth: The Voyager Interstellar Record (Random House, 1978). NASA also has information on the "Golden Record" here.
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