Our planet: The Blue Marble

On 7th December, 1972, the crew members of Apollo 17 spacecraft took a photograph of the Earth. This photograph, known as The Blue Marble, gives a clear idea as to why we know Earth as the Blue Planet. The earth’s surface contains more than 70 per cent water distributed in the oceans.

• • •

Volcano that shoots up cold liquid

A cryovolcano shoots up cold liquid instead of lava. This cold liquid known as cryomagma is a mixture of water and methane or ammonia. The cryomagma becomes solid as soon as it hits the surface. Cryovolcanoes are found on icy moons. The Sotra Facula volcano on Titan, the moon of Saturn, is a dormant cryovolcano.

• • •

Fish that turn into sleeping bags

The parrotfish are found in shallow coastal waters in the seas. Some parrotfish species cover themselves in a gelatinous substance especially at night before they sleep. This substance is produced by the fish from mucus from the glands located at the upper edge of the gill cavity. They form this protective sheath so that other fish of prey cannot smell them out at night.

• • •

How much of earth’s water is usable?

Only 3 per cent of earth’s water is fresh, the rest 97 per cent is salt water. Of that 3 per cent, over 2 per cent is frozen in ice sheets and glaciers. It means less than 1 per cent fresh water is found in lakes, rivers and underground. Water, indeed is a scarce resource.

• • •

Animals that can live longer without water than camels

Camels are known to live without water for many weeks in the desert. But it has been found that giraffes and kangaroo rats can live for more days than the camels. Giraffes eat food high in water content, and so they can live without water for weeks. Kangaroo rats never drink water but metabolise water from the seeds they eat.

• • •

Invention of the thermometer

In about 1607, Galileo invented an instrument that could measure the rise of water in a glass tube with the rise in temperature. This instrument is called a thermoscope. Later, scientists modified it to add a scale to mark the rise of water. Subsequently, water was replaced with alcohol and mercury.

• • •