ISRO’S Planetary Defence

(ISRO) Chairman S Somanath said last week that “we should be able to go and meet” the asteroid Apophis when it passes by Earth at a distance of 32,000 km in 2029. However, “it is yet to be decided in what way [ISRO] should participate”. The Indian space agency might send its own spacecraft, or collaborate with other space agencies. A NASA mission has already been confirmed. WHAT WOULD BE THE PURPOSE? Somanath’s remarks reveal ISRO’s intent to develop capabilities in planetary defence — an area it has so far not entered. ANY OTHER PURPOSE? A mission to study an asteroid would be the first step towards building a programme aimed at preventing celestial bodies from colliding with Earth with potentially catastrophic consequences. ABOUT APOPHIS When Apophis was discovered in 2004, scientists thought there was a 2.7% chance of a collision with earth — the highest probability of any large asteroid hitting Earth in the recent past. WHEN IS IT EXPECTED? Initial observations showed that if not in 2029, Apophis could hit Earth in 2036 or 2068. Its size & potential to cause damage: It measures about 450 m at its widest — a collision with Earth could cause large-scale damage. Some scientists compared the potential impact to the event that wiped out dinosaurs and most other extant life some 66 million years ago.

THE FACTS

POSSIBLE INCOMING THREATS FROM SPACE

Apophis may not pose a threat, but asteroids are headed towards Earth all the time. HOW FREQUENTLY THEY ENTER THE EARTH’S ATMOSPHERE? In fact, thousands enter the Earth’s atmosphere every day. Most are very small and Burn up in the atmosphere due to friction — some of the larger ones burn spectacularly, and show up as fireballs in the sky. In some cases, unburnt fragments make it to surface, although they are not large enough to cause much damage. THE ASTEROID ENCOUNTER IN RUSSIA In 2013, a 20-metre wide asteroid entered the atmosphere and exploded about 30 km above a Russian town, releasing energy equivalent to the blast yield of 400-500 kilotons of TNT — 26 to 33 times the energy released by the atom bomb that detonated over hiroshima. While most of this energy was absorbed by the atmosphere, shock waves travelled to the ground, flattened trees, damaged buildings, and injured 1,491 people, according to Russian Ministry of Health. WASN’T IT DETECTED? The asteroid was detected only after it entered the atmosphere. This was in part because it came from the direction of the Sun, and was hidden by its glare. Scientists know of at least 1.3 million asteroids. A planetary defence programme seeks to track and neutralise these threats.