One argument against the comet theory is that a comet would have left a large hole in the Earth's surface.

VOA: special.2009.01.20

Marc Rayman says Vesta appears to have a layered structure, one that is similar to planets like Earth, Mars and Venus.

VOA: special.2011.07.27

He promised to spend his remaining years in search of designs that could make human existence on Earth easier.

VOA: special.2010.05.30

Some cities and communities will hold Earth Day activities and celebrations for an entire week, not just on April twenty-second.

VOA: special.2010.04.21

Volcanoes on Mars suggest to Sam that the same kinds of processes that take place on Earth happen on other worlds.

VOA: special.2010.07.28

Newton proved his idea by measuring how much gravity force would be needed to keep the moon orbiting the Earth.

VOA: special.2011.06.01

But last month,a computer programmer from Australia made an exciting discovery of an unusual event in Earth's solar system.

VOA: special.2009.08.25

The demand for employees with green skills will continue to grow as the world seeks to become more earth friendly.

VOA: special.2009.09.04

Clay answered that no power on earth could force him to vote to establish slavery where it did not exist.

VOA: special.2009.03.19

The Everglades is the only place on Earth where fresh water alligators and saltwater crocodiles live in the same area.

VOA: special.2009.06.30

Back then,there was much hope that humans would return soon and make a home on Earth's only natural satellite.

VOA: special.2010.04.28

Nanodiamonds are produced under only a very high temperature and high pressure event, such as a comet striking Earth.

VOA: special.2009.01.20

Or they may bury them in the earth, place them in a tomb or scatter them in a special place.

VOA: special.2009.12.11

The first pictures of Earth taken from space showed a solid ball covered by brown and green landmasses and blue-green oceans.

VOA: special.2011.01.04