Ans: B

Exp: 

The Indian Space Research Organization (ISRO) is keen on participating in a planetary defence mission like NASA’s DART mission, in space ahead of a close shave for Earth with the Apophis asteroid on April 13, 2029.

About DART (Double Asteroid Redirection Test) mission:

• The DART (Double Asteroid Redirection Test) mission was initiated by NASA to demonstrate a method of deflecting an asteroid to protect Earth.
• Statement 1 is incorrect: Utilized the “kinetic impactor” technique, involving the collision of a spacecraft with an asteroid to alter its trajectory.
• Launched in November 2021, DART aimed to target the moonlet Dimorphos, orbiting the larger asteroid Didymos.
• DART aimed to validate the possibility of changing the trajectory of an asteroid by kinetic impactor technology.
• Statement 2 is correct: Successfully collided with Dimorphos on September 26, 2022, altering its orbit by 33 minutes, marking a significant milestone in planetary defense efforts.

Ans: C

Exp: 

A new study has revealed more spiral galaxies in the universe’s youth than astronomers had expected.

About galaxies:

• • Statement 1 is correct: Galaxy is a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction. They are the major building blocks of the universe.

• Types:

• Regular Galaxies:

• Spiral Galaxies: 

• • • • • Characteristics: Disc-shaped, greater concentration of stars near the center, nonuniform star distribution, old stars in the center, young stars in the arms, well supplied with interstellar gas for new star formation. 
        • Statement 2 is incorrect: The Milky Way is not an elliptical galaxy; it is a spiral galaxy.

• Elliptical Galaxies: 

• • • • • Characteristics: Most member stars are very old, no new star formation, smaller and less bright.

• Irregular Galaxies:

• • • Characteristics: Make up 1/10th of all galaxies, contain very old stars.
• Size Range: Smallest galaxies contain about 100,000 stars; largest contain up to 3,000 billion stars.

About Milky Way:

• The Milky Way is estimated to contain 100-400 billion stars. 
• The inner stars travel faster than those further out. 
• Statement 3 is correct: A supermassive black hole called Sagittarius A* is at the centre.
• The Solar System is located in the Orion Arm, 26,000 light years from the centre (about one-third from the centre) of the Milky Way.

Ans: B

Exp: 

A spike in air pollution in Indian cities that have clean air may raise death rates higher than in cities that have higher pollution loads. 

About PM (Particulate Matter) 2.5:

• • Statement 1 is incorrect: PM2.5 refers to fine particulate matter with a diameter of 2.5 micrometres or smaller.
  • Sources: PM2.5 is generated from various sources, including vehicle emissions, industrial processes, power plants, residential heating, and natural sources such as wildfires and dust storms.
  • Statement 2 is correct: Health Impacts: Due to their small size, PM2.5 particles can penetrate deep into the lungs and enter the bloodstream, leading to respiratory and cardiovascular diseases, aggravated asthma, and decreased lung function.
  • Environmental Impact: PM2.5 contributes to the formation of smog, which reduces visibility and has harmful effects on vegetation and ecosystems.

• Regulatory Standards:

• • The WHO recommends an annual mean PM2.5 concentration of no more than 10 µg/m³ and a 24-hour mean of 25 µg/m³.
  • Statement 3 is incorrect: India’s National Ambient Air Quality Standards (NAAQS): India has set an annual mean limit of 40 µg/m³ and a 24-hour mean of 60 µg/m³ for PM2.5, which are less stringent than the WHO guidelines.

Ans: B

Exp: 

A major icefield spanning the United States’ Alaska and Canada’s British Columbia could reach an irreversible tipping point sooner than predicted, with its glaciers rapidly receding since 2005, according to a new study. The researchers linked this with predominantly positive values in the Pacific Decadal Oscillation (PDO).

About Pacific Decadal Oscillation (PDO):

• • Statement 1 is correct: Definition: A long-term ocean fluctuation of the Pacific Ocean with phases lasting 20 to 30 years.
  • Phases:

• Warm or Positive Phase:

• • • • Statement 2 is correct: Sea surface temperatures (SSTs) are warmer than average along the western coast of North America.
      • Cooler SSTs in the central and western Pacific.
      • Associated with wetter conditions in the western US and Alaska.

• Cool or Negative Phase:

• • • • SSTs are cooler than average along the western coast of North America.
      • Warmer SSTs in the central and western Pacific.
      • Associated with drier conditions in the western US and Alaska.

• Impacts:

• • Influences marine ecosystems, fish populations, and climate conditions.
  • Alters precipitation patterns and temperature anomalies.
  • Affects the intensity and frequency of El Niño and La Niña events.
• Detection: Identified through statistical analysis of long-term sea surface temperature records in the North Pacific Ocean.
• Importance: Understanding PDO helps in predicting climate variations and managing water resources, fisheries, and agriculture.
• Statement 3 is incorrect: Unlike some climate oscillations like El Niño-Southern Oscillation (ENSO), which have relatively predictable cycles, the PDO does not have a regular or predictable pattern. It operates on decadal time scales but can vary in intensity, duration, and spatial extent. 

Ans: C

Exp: 

The 46th session of the UNESCO World Heritage Committee, which is being hosted by India from July 21-31, will be held at the Bharat Mandapam in New Delhi.

About UNESCO World Heritage Committee:

• The Committee operates under UNESCO and implements the World Heritage Convention. 
• Responsibilities include managing the World Heritage Fund and allocating financial aid upon member states’ requests.
• Statement 1 is correct: It consists of representatives from 21 States Parties elected by the General Assembly.
• Committee members serve six-year terms, although many opt for four-year terms to promote broader participation.
• The Bureau, elected annually, coordinates the Committee’s activities, setting meeting agendas and organising sessions.
• Statement 2 is correct: The Committee has the final authority to decide whether a property is listed on the World Heritage List.
• It reviews reports on the conservation status of listed properties and recommends actions for mismanaged sites.
• The Committee also decides on the inclusion or removal of properties from the List of World Heritage in Danger.
• India is set to chair UNESCO’s World Heritage Committee for the first time in 2024.