What is the Earth made of?

Genesis: Seeking Answers

We have often asked the questions, "What is the Earth made of?" " Where did we come from?" These has been the quiding lights for many space science missions designed to add to our knowledge base and ultimately answer our questions. We have sent satellites and probes to study many of the planetary bodies of our Solar System. We have sent astronauts into space and to the surface of the moon to collect samples to be examined. We have learned a lot but the question still remains unanswered. Maybe we should be asking a different set of questions.

How Did the Solar System Form?

Most scientists believe the solar system was formed 4.6 billion years ago by the gravitational collapse of the solar nebula, a cloud of interstellar gas, dust and ice created from previous generations of stars. It is thought that as time went on most of the gas and dust were pulled together by gravity to form the sun while other grains of ice and dust stuck to one another, eventually forming the planets, moons, comets, and asteroids as we know them today.

How this transition from solar nebula to planets took place has both fascinated and mystified scientists. Why did some planets, like Venus, develop thick, poisonous atmospheres, while others, like Earth, become hospitable to life? Partial answers are available from the study of the elemental and isotopic compositions of the solar system bodies which suggests that moons, planets, and even asteroids, are significantly different in composition. These objects are "fossil residues" and differences in basic elements and isotopic compositions provide invaluable insight into how the solar nebula evolved. Using these differences scientists can model various evolutionary processes, but we are hampered by one major issue -- we do not know what the original solar nebula was made of.

Looking at the Sun for Answers

Our Sun, which contains well over 99 percent of all the material in the solar system, may help us find the answer to the age old question. While its interior has been modified by nuclear reactions, the outer layers of the Sun are composed of very nearly the same material as the original solar nebula. Some of the Sun's composition can be determined by the characteristics of the light it emits, but the abundances of many elements and nearly all isotopes are as yet unknown.

Scientists are now redirecting their quest by asking "What is the sun made of? Are the Earth and planets made of the same stuff?"

The Sun's hot, turbulent surface prevents collecting a sample in the same way we would for a planet, but we can collect material flung from the sun, material we call the solar wind. By stationing a spacecraft outside Earth's magnetic field, this material can be captured and returned to Earth where high precision analyses can be carried out with some of the most sophisticated laboratory instruments in the world. Comparing the Sun's isotopic composition and abundances against known planetary composition data sets may provide another piece of the puzzle in our continuing search for origins.

What Genesis Can Help Us Find

NASA's Genesis mission will send a spacecraft to collect pieces of the sun, called solar wind, that may contain the answers. After a January 2001 launch, the Genesis spacecraft will be placed into orbit around L1, a point between Earth and the Sun where the gravity of both bodies is balanced. Once in orbit, Genesis will unfold its wing-like arrays and begin collecting particles of the solar wind that will imbed themselves in specially designed high purity wafers. After two years, the sample collectors will be re-stowed and returned to Earth. An exciting mid-air recovery of the sample return capsule will take place over the Utah desert. The samples will be stored and cataloged under ultra-pure clean room conditions and made available to the world scientific community for study for years to come.

Genesis Planned Trajectory

Science Objectives

• To obtain precise measures of solar isotopic abundances (Genesis will measure isotopic compositions of oxygen, nitrogen, and noble gases. These data will enable scientists to better understand the isotopic variations in meteorites, comets, lunar samples, and planetary atmospheres.)
• To obtain greatly improved measures of solar elemental abundances.
• To provide a reservoir of solar matter for 21st century science research, eliminating the need for future solar wind sample return missions.

Genesis' Mission Features

A number of mission features make Genesis an attractive as well as a viable endeavor.

• Samples are returned to Earth for study.
  Analytical instruments are on the ground and therefore do not need to meet space flight constraints.
• New data can be gathered as instruments continually evolve to the state of the art.
• Important results can be replicated.
• Mission design enables wide participation by international scientists.
• Mission design is simple
  Launch periods are flexible, not constrained by planetary alignments.
• A short, 3-month cruise means that 80 percent of the 3-year mission is devoted to science.
• No planetary encounters are planned.
• Spacecraft design is low risk
  Sun-oriented, spin stabilized, with fixed solar arrays
• Simple, passive thermal control with fixed antenna
• Low data rate, short range from Earth

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