Astronomy 5

Compared with the surface of the Earth, the surface of Venus is

almost completely flat and relatively smooth, except for two high volcanic mountain ranges.

The gas that is the major constituent of the atmospheres of Venus and Mars and a minor constituent of the Earth's atmosphere is

Carbon Dioxide

Roughly how much denser was Earth's second atmosphere (i.e., how much gas was there in it?) compared with today's atmosphere?

100 times denser

On a topographical map of Venus, how many large "continents" of high ground rise above the flat plains?

2

What significant evidence is there for the idea that large quantities of water once flowed on the planet Mars?

Deep, winding canyons and flood plains

The most common elements in the universe are

Hydrogen, helium, and traces of lithium

There is very little hydrogen or helium in the inner part of the solar system today. We believe the reason for this is that

Hydrogen, helium, and traces of lithium, the three lightest elements, were formed shortly after the creation of the universe. The heavier elements were produced much later by stars and are cast into space when stars die. By mass, 98% of the observed matter in the universe is hydrogen and helium.

What are the main characteristics of our solar system?

Hydrogen, helium, and traces of lithium, the three lightest elements, were formed shortly after the creation of the universe. The heavier elements were produced much later by stars and are cast into space when stars die. By mass, 98% of the observed matter in the universe is hydrogen and helium. The solar system formed 4.6 billion years ago from a swirling, disk-shaped cloud of gas, ice, and dust, called the solar nebula. The four inner planets formed through the accretion of dust particles into planetesimals and then into larger protoplanets. The four outer planets probably formed through the runaway accretion of gas and ice onto rocky protoplanetary cores over millions of years, but possibly by gravitational collapse in under 100,000 years.

Viking 1 and Viking 2, the planet-exploring spacecraft, were sent to which planet?

Mars

The smallest of the planets is

Mercury

The smallest planet in our solar system is

Mercury

The Martian moon Phobos orbits near the equatorial plane of Mars in just over 7.5 hours in the same direction as the planet rotation. How then would you see Phobos move across the Martian sky from the surface of the planet?

Phobos would rise in the west, move rapidly across the sky, set in the east, and appear several times per Martian day.

What is the Kuiper belt?

Pluto, once considered the smallest planet, has a size, density, and composition consistent with the known Kuiper Belt Objects (KBOs).

Observers in the nineteenth century reported seeing many straight-line features criss-crossing the surface of Mars and interpreted them to be canals constructed by intelligent beings. What is the most likely present-day explanation for these observations?

The lines were optical illusions caused by vague shadings on the planet's surface.

How does the temperature of Earth's atmosphere vary with height over the range 0-80 km?

The temperature decreases, then increases, then decreases again.

Why is the surface of Venus hotter than that of Mercury, even though Mercury is much closer to the Sun?

The thick carbon dioxide atmosphere of Venus has prevented re-emission into space of the heat absorbed from sunlight.

Which planet is the hottest one in the solar system, measured at the surface?

Venus

The presence of oxygen in Earth's atmosphere is thought to result directly from what type of process?

biological activity of plants and animals

Most of the craters on the Moon were formed by

bombardment by interplanetary meteoritic material.

The magnetic field of Earth is thought to be caused by

electric currents flowing in the electricity-conducting liquid core of Earth.

Where are the asteroids located?

found primarily between the orbits of Mars and Jupiter.

Which of the following events would NOT be a consequence of the destruction of the ozone layer on Earth?

large-scale freezing of the oceans

Spacecraft measurements near Venus indicate that the planet has

no planetwide magnetic field.

Hot-spot volcanism is a process that

produces gigantic volcanoes on Venus and Mars and chains of smaller volcanoes on the Earth (e.g., the Hawaiian Islands).

The asteroid belt is made up of

rocky bodies with diameters from less than a kilometer to hundreds of kilometers.

The supercontinent Pangaea is believed to have been

supercontinent on a tectonic plate that split into the present North and South America, Europe, and Africa

To what does the name Pangaea refer?

the result of a collision of continents, of a type that occurs roughly every 500 million years.

Examination of the whole surface of the Moon shows us that

there are two distinctly different sides, the side seen from Earth and the side hidden from Earth.

Mercury's atmosphere consists of

traces of hydrogen, helium, potassium, sodium, and oxygen.

Which unexpected chemical compound has recently been discovered on Mercury?

water ice at the north and south poles