Current Affairs MCQs – Page 47 (Q461-470)

Venus is the hottest planet in the solar system, with surface temperatures reaching around 465 degrees Celsius, hotter even than Mercury despite being farther from the Sun, due to its extremely thick atmosphere of carbon dioxide trapping heat through a runaway greenhouse effect. Its dense clouds are composed largely of sulfuric acid, making its surface conditions incredibly hostile. Mercury, Mars and Jupiter are tempting distractors, with Mercury being closer to the Sun but lacking a substantial atmosphere to trap heat as effectively as Venus. Venus is often called Earth's twin due to its similar size, though its climate is drastically different.

Mars is commonly known as the Red Planet due to the reddish appearance caused by iron oxide, or rust, covering much of its surface. It has long fascinated scientists and the public alike as a target for potential human exploration and past or present microbial life. Venus, Jupiter and Saturn are tempting distractors as other prominent planets, but none carries Mars's distinctive red coloring or nickname. Numerous robotic rovers, including NASA's Curiosity and Perseverance, have explored the Martian surface in search of evidence of ancient water and habitability.

Saturn is most famous for its prominent ring system, composed mainly of countless particles of ice and rock ranging from tiny grains to large chunks, extending thousands of kilometres from the planet itself. It is the second-largest planet in the solar system after Jupiter and is also a gas giant composed mainly of hydrogen and helium. Uranus, Jupiter and Neptune are tempting distractors, as each also has a much fainter ring system, but none rivals Saturn's spectacular and easily visible rings. Saturn's largest moon, Titan, is notable for having a thick atmosphere and lakes of liquid methane on its surface.

The solar system currently comprises eight planets, following the International Astronomical Union's 2006 decision to reclassify Pluto as a dwarf planet rather than a full planet, reducing the previous count of nine. The eight recognized planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, divided into rocky inner planets and gas or ice giant outer planets. Seven, nine and ten are tempting distractors, with nine reflecting the older, pre-2006 planetary count that included Pluto. Pluto remains classified today as a dwarf planet, alongside other similar objects like Eris, Haumea and Makemake.

The Sun is composed mainly of hydrogen and helium, the two lightest and most abundant elements in the universe, with hydrogen fusing into helium at the Sun's core through nuclear fusion, releasing the energy that powers sunlight and heat. This fusion process has sustained the Sun for roughly 4.6 billion years and is expected to continue for billions more. Oxygen and carbon, helium and carbon, and nitrogen and oxygen are tempting distractors, as each pair does exist in trace amounts within the Sun but does not represent its dominant composition. The Sun accounts for about 99.8 percent of the total mass of the entire solar system.

Columbia was the first NASA space shuttle to fly into orbit, launching on April 12, 1981, on mission STS-1, marking the beginning of the Space Shuttle program's three-decade run of orbital missions. The shuttle was designed as a reusable spacecraft, a significant departure from the single-use rockets and capsules used during the earlier Mercury, Gemini and Apollo programs. Discovery, Challenger and Atlantis are tempting distractors, as each was a later shuttle in NASA's fleet, with Challenger tragically lost in a 1986 launch disaster and Columbia itself later lost in a 2003 re-entry disaster. The Space Shuttle program officially ended in 2011 after 135 missions.

The Hubble Space Telescope was launched into orbit in 1990 aboard the Space Shuttle Discovery, becoming one of the most productive scientific instruments in history, providing stunningly detailed images of distant galaxies, nebulae and other cosmic phenomena. Its early images were initially blurry due to a flaw in its main mirror, later corrected by a dramatic 1993 servicing mission by astronauts. 1985, 2000 and 1995 are tempting distractors, with 1985 predating the telescope's actual launch and the others falling well after it. Hubble has operated for over three decades and continues to work alongside its successor, the James Webb Space Telescope, launched in 2021.

The chemical symbol for gold is Au, derived from the Latin word aurum, meaning shining dawn, reflecting the metal's lustrous appearance that has made it prized across human history for jewelry, currency and investment. Gold has an atomic number of 79 and is highly resistant to corrosion and tarnishing, making it useful in various industrial and electronic applications as well. Gd, Ag and Go are tempting distractors, with Gd actually representing the element gadolinium and Ag representing silver, both easily confused with gold's actual symbol. Gold has served as a store of value and medium of exchange across nearly every major civilization throughout history.

The chemical symbol for iron is Fe, derived from the Latin word ferrum, reflecting the metal's ancient importance in tool-making, construction and weaponry, giving its name to the historical Iron Age. Iron has an atomic number of 26 and is the primary component of steel, one of the most widely used structural materials in the modern world. Fr, Ir and In are tempting distractors, with Fr actually representing the element francium, Ir representing iridium, and In representing indium, all easily confused with iron's actual symbol. Iron is also essential to human biology, forming a key component of hemoglobin, the protein that carries oxygen in the blood.

The chemical symbol for sodium is Na, derived from the Latin word natrium, reflecting the element's historical association with natural mineral deposits such as sodium carbonate. Sodium has an atomic number of 11 and is a highly reactive alkali metal that must be stored away from water and air to prevent violent reactions. S, So and Sd are tempting distractors, with S actually representing the element sulfur, easily confused with sodium's less obvious symbol. Sodium is essential for human health, playing a critical role in nerve function and fluid balance, and is most commonly consumed as part of table salt, sodium chloride.