Lessons from Our Past
By understanding how life formed on Earth, astrobiologists hope to find clues on how to find life elsewhere. Biologists have long believed that Earth formed with only simple inorganic molecules such as hydrogen, methane, and ammonia in its atmosphere and crust. It was thought that energy from lightning storms instigated the creation of the complex organic molecules containing carbon, hydrogen, oxygen, nitrogen, potassium, and sulfur (CHONPS) that are attributed to life on Earth. But recent discoveries are opening minds to other possibilities.
It has previously been believed that our Solar System began from a cloud of simple molecular gas, and only as Earth evolved did complex organic molecules form. However, recent observations of the atmospheres around old carbon stars show the existence of organic molecules. As these stars die, they spew organic molecules out into the interstellar medium where new stars form. The formation of a new star may include a planetary system with Earth-like planets that in turn will contain organic molecules right from the start.
Another theory points to a Martian meteorite, known as ALH84001, discovered in an ice field in Antarctica. Although this 4.2 pound piece of rock is thought to have landed on Earth about 13,000 years ago, it was ejected from Mars 16 million years ago and radioactive dating shows that it formed about 4 billion years ago at a time when Mars was much warmer and wetter.
Observations by the Mars Global Surveyor indicate areas of liquid water run-offperhaps even in the very recent past. In this image it appears that water has seeped from beneath the Martian surface and run down the steep gully walls. Image courtesy of NASA/JPL/Malin Space Science Systems.
The Search Is On
To find life elsewhere, we must first find homes for life on Earth. Mars has long been a place of study, originally because of it being our neighbor and thus the fodder for many a science fiction story, but also when the surface of Mars was photographed and mapped by spacecraft beginning with Mariner, those stories became more than fantasy. Channels on the surface of Mars seem to give clear evidence that water once flowed there and that the planet was once much warmer than it is now.
The Galileo spacecraft sent to explore Jupiter has rekindled great interest about the possibility of life on its satellite, Europa. A large ocean of liquid water is thought to exist under the moons icy surface as evidenced by the recently discovered periodic fluctuations of Europas magnetic field. Regions of "chaotic" terrain may represent periodic episodes of crustal melting, which could allow for the exchange of nutrients and gases necessary for the propagation of simple life forms. There is also evidence that the ice layer covering the ocean may be fairly thin, only one or two kilometers thick. This can be inferred from the cycloidal crack patterns that scientists have determined are caused by Jupiters intense tidal pull.
is known to exist in Europan-type conditions on Earth, and studies of Lake Vostok
will enlighten future explorations for life in our Solar System. In addition,
the Cassini spacecraft is hurtling toward Saturn where in 2004 it will
be able to examine the ringed-planets large moon Titan, long a prime site
for scientists speculation about life.
Europas complicated surface appears to betray the presence of an ocean of water beneath the ice. In this image from the Galileo spacecraft, the ridged plains are likely evidence of cracking and then refreezing of the Jovian moons icy surface. If there is, indeed, a deep ocean under the ice, do conditions for at least unicelluar life obtain on Europa? Image courtesy of NASA.
Astrobiologists are spreading their wings and searching in many different modes, for many different possible types of life. One of the most exciting is the Search for Extraterrestrial Intelligence (SETI). Since the early 1960s, a small group of astronomers has been searching the skies for a signal from another civilization. In 1994, Congress cut the government funding for this research, and a new effort, Project Phoenix, rose from the ashes with support from private funding. Currently, Project Phoenix is monitoring Sun-like stars over a range of radio frequencies and is looking for a signal that is limited to one very narrow-band frequency. This type of signal would almost certainly have to be sent deliberately as opposed to being caused by a natural phenomenon.
What Does the Public Have to Learn from All This?
The research scientists arent the only ones getting excited about astrobiology. This new discipline has tremendous potential for revolutionizing science education. It is rich with exciting content to engage those who generally dont consider themselves scientifically-oriented, and also for opening the ears and minds of adults who may want a new reason to visit their local science center.
High school courses have traditionally been compartmentalized into biology, chemistry, physical or earth science, and perhaps physics or an elective such as astronomy or oceanography. This may, in the best of cases, prepare students for the "almighty test," but does it really prepare students for scientific literacy and logical decision-making? In many cases, the current educational system is failing to prepare students even for its own tests because students interest and engagement in science is waning. They see no connection between what is taught in textbooks and what they value in their own lives.
Science in the real world is integrated and problem-based. We need to "hook" students. We need to offer a course so inherently interesting, and, yes, even mysterious, that students will open their minds and let us insert a gentle wedge to begin the learning process. Astrobiology is such a subject, a portal to understanding broad scientific concepts in a context that is immediately exciting and intriguing for students.
Full-year astrobiology courses in the works include the integrated high school science curriculum "Astrobiology: The Search for Life," being developed by TERC and NASA (astrobio.terc.edu), and another, written around the theme of evolution by the SETI Institute and NASA, "Voyages Through Time" (www.seti-inst.edu/education/vtt-bg.html). In addition, the Center for Educational Technologies at Wheeling Jesuit University, in conjunction with the NASA Classroom of the Future, is producing a software program called "Exoquest" (http://www.cotf.edu/ExoQuest/) for grades 79 that will create a link between students and scientists to pursue investigations in different areas of astrobiology research. A new Ph.D. program has also been created at the University of Washington, Seattle, specializing in astrobiology (depts.washington.edu/astrobio).
These are just a few of what will be a wave of exciting educational opportunities. The courses and programs meet the challenge of preparing young people for new types of research, those that require multiple perspectives and integrated problem-solving skills. They are also just in time to prepare the next generation to use the rapidly advancing technology that will allow us to unravel many of the puzzles the Universe offers us. It is only a matter of time until one of these well-prepared students discovers the first evidence that we are not alone.
Jodi Asbell-Clarke is a scientist and senior curriculum developer at TERC and Jeff Lockwood is the director of TERCs Astrobiology Curriculum project. For more information on the TERC Astrobiology Curriculum, please visit astrobio.terc.edu or contact the authors by post at TERC, The Astrobiology Curriculum, 2067 Massachusetts Avenue, Cambridge, MA 02140, or by email at email@example.com and firstname.lastname@example.org
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