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Prenektarski period

The geologic history of Earth's Moon has been divided into five broad time periods, or systems. From oldest to youngest, these are pre-Nectarian, Nectarian, Imbrian, Eratosthenian, and Copernican. These systems are defined by the number of impact craters on the ground surface (more craters = older surface) correlated to the absolute ages determined for the lunar rock samples returned to Earth by the U. S. Apollo missions and unpiloted Soviet Luna missions. The pre-Nectarian system extends from 4. 5 billion to 3. 9 billion years ago.

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Saistītie termini

period
Physics; General physics

The time required for one complete cycle of a wave.

period
Art history; Visual arts

An extended interval of time, understood usually within the context of an identifiable geographic region, characterized by a specific set of cultural, economic, social or ...

adaptacioni period
Psychology; Behavior analysis

The phase in a behavior analysis program during which adaptation takes place. This can be assumed when behavioral patterns stabilize.

period kriticki
Psychology; Behavior analysis

The time during which a stimulus can become imprinted . More generally, any time period to which the operation of some behavioral process is limited.

period poluraspada
Astronomy; Planetary science

The amount of time required for half of the mass of a radioactive isotope to decay.

Ceres
Astronomy; Planetary science

The largest of the known asteroids; a dwarf planet. Also called 1 Ceres because it was the first asteroid to be discovered (by Piazzi in 1801).

Jarkovski efekat
Astronomy; Planetary science

An explanation for the shift in an asteroid's orbit around the Sun due to a thermal thrust caused by the body's uneven heating by sunlight. The illuminated side of an asteroid ...

Viking
Astronomy; Planetary science

U. S. Mission to Mars, composed of two spacecraft, launched in 1975. Viking 1 and Viking 2 both consisted of an orbiter and a lander. Primary mission objectives were to obtain ...

sublimacija
Astronomy; Planetary science

Phase transformation from solid to gas.

Misija Stardust
Astronomy; Planetary science

The fourth in NASA's Discovery program of low-cost spacecraft with highly focused science goals, Stardust was comprised of a spacecraft and capsule that completed a seven-year, ...

Solarna i heliosfericna observatorija
Astronomy; Planetary science

A project of international collaboration between ESA and NASA to study the Sun from its deep core to the outer corona and the solar wind. SOHO was launched in December, 1995. SOHO ...

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