Station 1: Earth as a Habitat - From Origin to Present

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WHY IS EARTH WET AND ALIVE?

Our blue Earth is shown with its lifeless Moon. Impacts pummeled the early Earth (and Moon) before life emerged.The Moon preserves a record of those events because it lacks an atmosphere and plate tectonics. Impacts also affected Mars and other planets.

Earth is unique within our Solar System — wet and teeming with life. How did life begin here? How has the environment changed since Earth’s formation? Why is Earth a life-sustaining habitat now? Can life exist elsewhere in the Solar System and in the Universe? This “walk through time” illustrates critical steps along the pathway to life today, and scientific efforts at Goddard to address them.

THREE DOMAINS OF LIFE

Life and its Instruction Codes:All living organisms store an instruction set (DNA, background) used in reproduction and function. The DNA molecule is made of hydrogen, oxygen, nitrogen, carbon and phosphorus.

Astrobiologists define life as cell-based organisms that can reproduce and evolve. These include single-celled organisms such as bacteria and archaea that could survive in extreme environments on early Earth and now. Scientists search for pathways that could lead from chemical mixtures to the basic building blocks of living organisms.

THE SPIRAL TIMELINE

The spiral represents the timeline of Earth history from its formation about 4.6 billion years ago to the present. Each station in this exhibit describes a different epoch and has a distinctive 3D iconic object above the station and on the spiral. The number of a station (2, 3, ...) identifies the order of its appearance in this Astrobiology Walk.

THE COSMIC PROGRESSION TOWARDS LIFE

Life is the product of nearly 14 billion years of cosmic evolution. Atoms formed as the Universe cooled following the Big Bang, then stars and galaxies, planets and life. The Big Bang produced atoms of hydrogen, helium and lithium, the lightest elements. Other elements were made inside the first stars, but formation of the heavier elements required cycling through many generations of stellar birth and death. The Earth and life as we know it required this heritage — you are made of star stuff! Thus, the cosmos evolved towards greater complexity in a progression that enabled the emergence of life.

A COSMIC TIMELINE TOWARDS LIFE
WHAT EXACTLY IS ASTROBIOLOGY?

Astrobiology is a multidisciplinary science that involves astronomy, biology, chemistry, geology and physics. Researchers of the Goddard Center for Astrobiology study the origin and formation of the building blocks of life in extraterrestrial environments, and examine whether the delivery of these primordial materials and water to the early Earth enabled the emergence and evolution of life. They also extend these studies to other planets and moons, and to other planetary systems.

If the history of the Universe were compressed into one year with the Big Bang occurring on January 1st, Earth would be formed in mid-September, microorganisms in early October, multicellular life in early December, and Homo sapiens (humans) on December 31st.

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