Why we explore Mars—and what decades of missions have revealed

What gas is mainly found in Mars' atmosphere?

• Oxygen

• Carbon Dioxide

• Hydrogen

• Nitrogen

Answer explanation

LIne 9: Unfortunately, the planet is now wrapped in a thin carbon dioxide atmosphere and cannot support earthly life-forms.

How long is a year on Mars?

• 365 days

• 687 days

• 700 days

• 1300 days

Answer explanation

LIne 5: That’s why one year on Mars lasts for 687 Earth days, while a day on Mars is just 40 minutes longer than on Earth.

What features on Mars indicate that there was once water?

• Mountains

• Rivers and valleys

• Desert

• Forests

Answer explanation

LIne 17: they see features that are unquestionably the work of ancient, flowing liquids: branching streams, river valleys, basins, and deltas.

Why can't Mars support Earth-like life today?

• It is too cold

• It has too much water

• It has a thin atmosphere

• It is too big

Answer explanation

Line 9:  Unfortunately, the planet is now wrapped in a thin carbon dioxide atmosphere and cannot support earthly life-forms.

Mars is smaller than Earth.

• True

• False

Answer explanation

Line 3: It is just a smidge more than half of Earth’s size.

Mars is the ____ rock from the sun, just after earth.

• Fifth

• Fourth

• Second

• Third

Answer explanation

Line 3: Mars is the fourth rock from the sun, just after Earth.

How does Mars’ gravity compare to Earth’s?

• It is stronger than Earth’s gravity.

• It is weaker, at 38% of Earth’s gravity.

• It is the same as Earth’s.

• It varies widely across the planet.

Answer explanation

Line 4: with gravity only 38 percent that of Earth’s.

Why is water not accessible on Mars?

• It evaporates too quickly.

• It is too deep underground.

• It is locked in polar ice caps and beneath the surface.

• There is no water present at all.

Answer explanation

Line 11: Although water does exist on Mars, it’s locked into the planet’s icy polar caps and buried, perhaps in abundance, beneath the Martian surface.

The planet’s land area is roughly equal to the Earth’s continents.

• True

• False

Answer explanation

Line 7: Despite its smaller size, the planet’s land area is also roughly equivalent to the surface area of Earth’s continents.