IAS Gyan

Daily News Analysis


2nd April, 2024 Science and Technology


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An international team of scientists, including researchers from India, conducted the study that led to the discovery of ozone on Callisto.



  • Chemical Evolution of SO2 Astrochemical Ice: The study focused on investigating the chemical evolution of SO2 astrochemical ice under ultraviolet irradiation, simulating conditions similar to those on Callisto's surface.
  • Experimental Setup: Scientists conducted experiments at the National Synchrotron Radiation Research Centre (NSRRC) in Taiwan, using vacuum ultraviolet photons to mimic solar radiation. They deposited sulphur dioxide ice samples onto a substrate of lithium fluoride in a chamber with very low pressure to recreate outer space conditions.
  • Observation and Analysis: The team carefully monitored the sulphur dioxide ice samples' temperature, irradiating them with vacuum-ultraviolet photons and recording their ultraviolet absorption spectrum during and after irradiation using a photomultiplier tube detector.
  • Detection of Ozone: Analysis of the absorption spectrum revealed a distinct signature indicating the formation of ozone after irradiating the sulphur dioxide ice samples. This discovery provides strong evidence for the presence of ozone on Callisto's surface.


  • Ozone as Indicator of Atmospheric Stability: The presence of ozone on Callisto suggests the existence of stable atmospheric conditions on the moon. Ozone formation requires specific chemical processes and stable environmental conditions, indicating the potential for habitable environments.
  • Fundamental Ingredient for Life: Oxygen, a component of ozone, is essential for the formation of complex molecules necessary for life as we know it, such as amino acids. The discovery raises questions about the habitability of Callisto and other icy moons in our solar system.
  • Insights into Geological and Atmospheric Processes: The discovery of ozone and other unidentified bands in the absorption spectrum provides valuable insights into the geological and atmospheric processes occurring on Callisto and other icy moons. It enhances our understanding of the formation and evolution of Jupiter's moons.
  • Comparative Planetary Science: Comparing the chemical compositions and processes on different celestial bodies, such as Callisto and Ganymede, helps scientists better understand the similarities and differences between these moons and their potential habitability.

About Ozone

  • Ozone is a molecule composed of three oxygen atoms (O3) and is found in two main regions of the Earth's atmosphere: the stratosphere and the troposphere.
  • It plays crucial roles in both regions, with significant implications for life on Earth.

Properties of Ozone:

  • Chemical Formula: O3
  • Molecular Weight: Approximately 48 g/mol
  • Physical State: Ozone is a pale blue gas at room temperature with a distinct odor.
  • Solubility: It is sparingly soluble in water.

Distribution in the Atmosphere:

  • Stratospheric Ozone: The stratosphere, located approximately 10 to 50 kilometers above the Earth's surface, contains the ozone layer. This layer absorbs and scatters the majority of the Sun's harmful ultraviolet (UV) radiation.
  • Tropospheric Ozone: Ozone also exists in the troposphere, the lowest layer of the Earth's atmosphere, where it is considered a pollutant and a key component of photochemical smog.

Formation of Ozone:

  • Stratospheric Ozone Formation: Ozone in the stratosphere is primarily formed through the photodissociation of oxygen molecules (O2) by solar ultraviolet radiation, followed by the recombination of oxygen atoms (O) with oxygen molecules.
  • Tropospheric Ozone Formation: Tropospheric ozone is formed through complex photochemical reactions involving nitrogen oxides (NOx), volatile organic compounds (VOCs), and sunlight.

Roles and Functions:

  • UV Protection: In the stratosphere, ozone absorbs and scatters the majority of the Sun's harmful UV radiation, protecting life on Earth from its adverse effects such as skin cancer, cataracts, and immune suppression.
  • Climate Regulation: Ozone also contributes to the regulation of the Earth's climate by absorbing infrared radiation emitted by the Earth's surface, thereby influencing the energy balance of the atmosphere.
  • Tropospheric Oxidant: Tropospheric ozone acts as a powerful oxidant, influencing atmospheric chemistry, and playing a role in the formation and behavior of other air pollutants.

Ozone Depletion:

  • Stratospheric Ozone Depletion: Human activities, particularly the release of chlorofluorocarbons (CFCs), halons, and other ozone-depleting substances (ODS), have led to the thinning of the ozone layer, especially over the polar regions, resulting in the formation of the ozone hole.
  • Impacts of Ozone Depletion: Ozone depletion increases the amount of UV radiation reaching the Earth's surface, leading to adverse effects on human health, ecosystems, and the environment.

Tropospheric Ozone Pollution:

  • Sources: Tropospheric ozone is mainly produced by the reaction of NOx and VOCs in the presence of sunlight. Anthropogenic sources include vehicle emissions, industrial processes, and combustion of fossil fuels.
  • Health Effects: Exposure to elevated levels of tropospheric ozone can lead to respiratory problems, cardiovascular issues, and exacerbation of existing lung diseases such as asthma.
  • Environmental Impacts: Tropospheric ozone can damage vegetation, reduce crop yields, and impair ecosystems by affecting plant physiology and reducing photosynthetic activity.

Mitigation Strategies:

  • Regulation: International agreements such as the Montreal Protocol regulate the production and consumption of ozone-depleting substances to prevent further depletion of the ozone layer.
  • Air Quality Management: Measures to reduce emissions of NOx and VOCs from vehicles, industries, and other sources can help mitigate tropospheric ozone pollution.
  • Technological Solutions: Adoption of cleaner technologies, such as catalytic converters in vehicles and low-emission industrial processes, can help reduce ozone precursor emissions.

About Jupiter

  • Jupiter, the largest planet in our solar system, is a gas giant composed mostly of hydrogen and helium.
  • It's a fascinating celestial body with unique features, including its massive size, powerful magnetic field, iconic bands of clouds, and swirling storms.

Characteristics of Jupiter:

  • Size and Mass: Jupiter is the largest planet in the solar system, with a diameter of about 139,822 kilometers (86,881 miles) and a mass approximately 318 times that of Earth. Its volume is over 1,300 times greater than Earth's.
  • Orbit: Jupiter orbits the Sun at an average distance of about 778 million kilometers (484 million miles), taking approximately 11.86 Earth years to complete one orbit.
  • Rotation: Jupiter has a rapid rotation period of about 9.9 hours, making it one of the fastest-spinning planets in the solar system.
  • Magnetic Field: Jupiter possesses an extremely powerful magnetic field, about 14 times stronger than Earth's. This magnetic field generates intense radiation belts, posing a significant hazard to spacecraft.
  • Atmosphere: Jupiter's atmosphere is predominantly composed of hydrogen (about 75%) and helium (about 24%), with traces of other elements and compounds. It exhibits colorful cloud bands, zones, and belts caused by differential wind speeds and chemical composition.

Composition and Structure:

  • Core: Jupiter likely has a solid core made of heavy elements, possibly surrounded by a layer of metallic hydrogen under immense pressure.
  • Atmospheric Layers: The atmosphere consists of several layers, including the troposphere, where most weather phenomena occur, and the stratosphere, mesosphere, and thermosphere, extending outward.
  • Clouds: Jupiter's clouds are primarily composed of ammonia crystals, sulfur, and other compounds. Prominent features include the Great Red Spot, a massive storm system larger than Earth, and other smaller storms.


  • Galilean Moons: Jupiter has four large moons discovered by Galileo Galilei in 1610: Io, Europa, Ganymede, and Callisto. These moons are some of the most intriguing objects in the solar system, with diverse features such as volcanoes, subsurface oceans, and potential for habitability.
  • Other Moons: Jupiter has many smaller moons, totaling over 70 known satellites. Some are irregularly shaped captured asteroids or fragments, while others are relatively large and have unique characteristics.

Exploration History:

  • Pioneer and Voyager Missions: NASA's Pioneer 10 and 11 spacecraft conducted flybys of Jupiter in the 1970s, followed by the Voyager 1 and Voyager 2 missions in 1979, which provided detailed images and data of the planet and its moons.
  • Galileo Mission: Launched in 1989, the Galileo spacecraft orbited Jupiter from 1995 to 2003, conducting extensive studies of the planet and its moons. It discovered subsurface oceans on Europa and evidence of volcanic activity on Io.
  • Juno Mission: NASA's Juno spacecraft arrived at Jupiter in 2016 and entered orbit to study the planet's atmosphere, magnetic field, and interior structure in unprecedented detail. Juno's mission aims to improve our understanding of Jupiter's formation and evolution.

About Moons of Jupiter

  • Jupiter, the largest planet in our solar system, boasts a remarkable collection of moons, with over 79 known natural satellites as of current observations.
  • Among these, the four largest moons, known as the Galilean moons, were discovered by Galileo Galilei in 1610.
  • These moons—Io, Europa, Ganymede, and Callisto—have fascinated astronomers and scientists for centuries due to their diverse geological features, potential for subsurface oceans, and possible habitability.

Galilean Moons:

  • Io:
    • Io is the innermost of the Galilean moons and the most volcanically active body in the solar system.
    • It has over 400 active volcanoes, spewing sulfur and other volcanic materials across its surface.
    • Io's volcanic activity is driven by tidal heating generated by its interaction with Jupiter and other Galilean moons.
    • Its surface is covered with colorful sulfur compounds, lava flows, and mountains.
  • Europa:
    • Europa is one of the most intriguing moons in the solar system, with a smooth, icy surface crisscrossed by cracks and ridges.
    • It is believed to have a subsurface ocean beneath its icy crust, making it a prime target in the search for extraterrestrial life.
    • Geysers of water vapor have been observed erupting from its surface, indicating the presence of subsurface water.
    • Europa's ocean may contain twice the amount of water found on Earth and could harbor conditions suitable for life.
  • Ganymede:
    • Ganymede is the largest moon in the solar system, even larger than the planet Mercury.
    • It has a complex geology, with grooved terrain, impact craters, and large dark regions known as 'mare'.
    • Ganymede is the only moon known to have its own magnetic field, likely generated by a liquid iron-nickel core.
    • Evidence suggests Ganymede also has a subsurface ocean beneath its icy crust, possibly making it another candidate for habitability.
  • Callisto:
    • Callisto is the outermost of the Galilean moons and one of the most heavily cratered bodies in the solar system.
    • Its surface features impact craters of various sizes, suggesting a lack of significant geological activity.
    • Callisto's surface is composed of a mixture of water ice and rocky material.
    • While Callisto likely has a subsurface ocean, it is thought to be in contact with a rocky core rather than being kept warm by tidal heating.

Other Notable Moons:

  • Amalthea:
    • Amalthea is one of Jupiter's innermost moons and one of the reddest objects in the solar system.
    • It has an irregular shape and orbits close to Jupiter, within its main ring system.
    • Amalthea may be a captured asteroid or a fragment of a larger moon disrupted by tidal forces.
  • Himalia Group:
    • This group includes several irregularly shaped moons orbiting Jupiter at a considerable distance.
    • The largest member, Himalia, is about 170 kilometers in diameter and likely captured asteroids.
  • Prograde and Retrograde Moons:
    • Jupiter has both prograde (orbiting in the same direction as the planet's rotation) and retrograde (orbiting in the opposite direction) moons.
    • These moons have diverse sizes, shapes, and orbital characteristics, reflecting their varied origins and histories.


  • Galileo Mission: NASA's Galileo spacecraft provided detailed observations of Jupiter's moons during its mission from 1995 to 2003, including multiple flybys of the Galilean moons.
  • Juno Mission: While primarily focused on studying Jupiter itself, NASA's Juno spacecraft has also provided valuable data on the planet's magnetosphere, which interacts with its moons.
  • Future Missions: Planned missions, such as NASA's Europa Clipper and the European Space Agency's JUpiter ICy moons Explorer (JUICE), aim to explore Jupiter's moons in greater detail, focusing on Europa's potential habitability and the geology of Ganymede and Callisto.


Q.  Ozone is a vital component of the Earth's atmosphere, serving critical roles in protecting life from harmful UV radiation, regulating climate, and influencing atmospheric chemistry.  Critically Analyse. (250 Words)