About how much of Earth's surface is covered by water?
AnswerAbout 71%
Oceans, seas and other water bodies cover roughly 71% of Earth's surface.
Nature · Facts & stats
Earth facts & stats
7 fact-checked facts about planet Earth, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
What is Earth's only natural satellite?
AnswerThe Moon
The Moon is Earth's single natural satellite; Phobos orbits Mars.
Going deeper
Which gas makes up about 78% of Earth's atmosphere?
AnswerNitrogen
Dry air is about 78% nitrogen and 21% oxygen.
Which unit of length, about 150 million km, is roughly the average Earth-Sun distance?
AnswerAn astronomical unit
The astronomical unit (au) is fixed at about 149.6 million km, roughly Earth's average distance from the Sun.
Earth Day, first held in 1970, is observed on which date?
AnswerApril 22
Earth Day is marked each year on April 22; June 5 is World Environment Day.
Expert level
About how old is Earth?
Answer4.54 billion years
Radiometric dating of meteorites and old minerals puts Earth's age at about 4.54 billion years.
In which layer of the atmosphere is most of the ozone layer found?
AnswerStratosphere
About 90% of atmospheric ozone lies in the stratosphere, where it absorbs much of the Sun's UV light.
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