ARE THERE PLANETS SIMILAR TO THE EARTH????
Three planets, Mercury, Venus, Mars, resemble the Earth to some extent. They are made up of rocks, and have a similar structure consisting of the crust, mantle, and core. Moreover, they are relatively close to the sun, and hence are not ice-cold; except for Venus, all of them have seasons. Nevertheless, these planets are very different from the Earth. Mercury, covered with craters, and Mars, sometimes called the ‘little brother of the Earth’, have a very thin atmosphere; the brightly shining Venus has an atmosphere much denser than that of the Earth. Even Pluto, which is far away from the sun and consists mainly of rocks, is quite different from the Earth.
MERCURY HAVE SO MANY CRATERS
Mercury has a very thin atmosphere. Consequently, meteorites-unlike the chunks of rocks falling upon the Earth-are not slowed down by atmospheric pressure when they fall on the planet. The sun attracts many other heavenly bodies because of its huge mass, and since Mercury is very near to the sun, many of these meteorites fall on its surface without any resistance and create craters. The largest crater is the round Mare Caloris, which is 9km deep and 1400km wide. The impact of the meteorite was so strong that it shook the opposite side of the planet and created many scattered trenches on its surface.
WHY DOES VENUS SHINE SO BRIGHTLY????
As Venus is not a star, it does not shine by its own light. But its unusually dense atmosphere reflects the sunlight so effectively that it seems to radiate in space. It is thus one of the brightest of the heavenly bodies in the night sky. The dense, opaque atmosphere is also the reason why scientists were for long unable to study the surface of Venus. Only radar beams could penetrate through the gas cover. The probe ‘Magellan’ worked with radar beams and prepared the first complete map of the surface of Venus after 1990. We now know that Venus has lowlands and highlands as well as some canyons on its surface.
WHY IS MARS CALLED THE EARTH’S ‘LITTLE BROTHER’????
Mars is so called because among all the planets of the solar system it resembles the Earth the most. Our neighbouring planet rotates at the same speed as the Earth. It means that one day on Mars is approximately the same as one day on the Earth. Mars has seasons too. Even the landscape is similar to that of the Earth. The Mars landscape is a dry, rocky surface coated with fine red dust. Traces of water, and at least some land features that may have been shaped by water, have too been discovered. The highest mountain of the solar system, the 26km high volcano Olympus Mons, is on Mars, as is the largest canyon of our solar system, the 4000km long and 200km wide Valles Marineris. Even the rocks on Mars are similar to the ones found on the Earth. We know this because small robots such as the Sojourner sent to Mars have sent back reports about its surface.
DID YOU KNOW THAT?????
•MARS APPEARS RED IN THE SKY. THUS, IT IS ALSO CALLED THE ‘RED PLANET’. THE RED COLOUR COMES FROM THE IRON OR - TO BE MORE PRECISE-RUST-CONTAINING ROCKS ON ITS SURFACE.
•THE SAILOR JAMES COOK OBSERVED THE 1769 TRANSIT OF VENUS THE PACIFIC ISLAND OF TAHITI..