Juno is a NASA spacecraft in orbit around Jupiter, the largest planet in the solar system.
Its instruments read the planet’s interior, atmosphere and magnetic field from a polar orbit.
Must Know
The Juno Mission at a Glance
What Juno is
- DefinitionJuno is a robotic probe built by Lockheed Martin and flown by NASA’s Jet Propulsion Laboratory.
- ProgramIt flies under NASA’s New Frontiers programme for medium-class planetary missions.
- LaunchThe spacecraft lifted off from Cape Canaveral on 5 August 2011.
- ArrivalJuno entered Jupiter’s orbit on 4 July 2016 after a five-year cruise.
The polar orbit
- ShapeJuno swings around Jupiter on a highly elliptical polar orbit.
- PerijoveEach close pass skims about 4,200 km above the cloud tops.
- ApojoveEach swing then carries it far beyond the orbit of Callisto.
- PeriodThe orbit takes about 53 days to complete once.
- WhyThe poles and the deep interior stay visible from this orbit.
Solar power at Jupiter
- DistanceJupiter sits about five times farther from the Sun than Earth.
- LightThe planet receives only about one-twenty-fifth of Earth’s sunlight.
- FirstJuno is the first Jupiter mission powered by solar arrays.
- SizeIts three solar wings stretch roughly the size of a basketball court.
- LessonThe mission proved solar power works even at Jupiter’s distance.
What Juno measures
- WaterA microwave radiometer probes the deep atmosphere and its water.
- GravityRadio tracking maps the planet’s gravity field with great precision.
- MagnetismMagnetometers chart the structure of Jupiter’s magnetic field.
- AurorasUltraviolet and particle sensors study the polar auroras.
- InteriorTogether these data reveal the planet’s core and interior.
Good to Know
Reading Jupiter’s Hidden Interior
The fuzzy core
- QuestionDid Jupiter grow around a solid, compact core?
- DataJuno’s gravity maps show the core is not sharp-edged.
- DiluteThe core looks dilute, with heavy material mixed deep into hydrogen.
- MeaningThis supports the core-accretion story of planet birth.
Water and planet formation
- MeasureJuno’s microwave data put equatorial water near three times the Sun’s oxygen.
- MeaningHigh water suggests Jupiter captured icy building blocks early.
- ModelThe amount of water tests how and where planets formed.
- EarthThe same icy material may have delivered water to Earth.
The lumpy magnetic field
- ExpectationScientists expected a simple, bar-magnet style field.
- FindingJuno found a field that is stronger and lumpier than expected.
- Blue SpotA strong patch near the equator is called the Great Blue Spot.
- DynamoThe field seems to grow from deep circulating hydrogen.
Winds that run deep
- BeltsJupiter’s coloured belts and zones are its visible weather.
- DepthJuno’s gravity data show the winds extend about 3,000 km down.
- ResultThe visible bands are shallow skin on a deep, rotating interior.
Polar cyclones
- PolesJuno found clusters of cyclones circling both poles.
- NumbersEight storms ring the north pole and five the south.
- PentagonThe southern storms sit in a stable pentagon pattern.
- SurpriseTheir stability over years still puzzles planetary scientists.
Test Yourself
Great to Know
From Jupiter to Earth: Planetary Origins
Why Jupiter is a fossil
- FirstJupiter likely formed first among all the planets.
- MassIt holds more material than every other planet combined.
- LeftoversThe giant gathered most of the solar system’s leftover building blocks.
- RecordIts composition therefore records the early solar nebula.
What Jupiter tells us about Earth
- BuildingJuno’s water data reveal what the young solar system could supply.
- WaterEarth’s oceans may trace back to the same icy building blocks.
- DeliveryComets and asteroids carried water to the inner planets.
- LinkJupiter’s gravity shaped how material moved through the early system.
Testing formation models
- Core AccretionIn this model, a rocky core grows first, then pulls in gas.
- RivalGravitational instability needs a collapsing gas clump instead.
- VerdictJuno’s dilute core and water fit the core-accretion path.
- TimingThat model says giant planets formed within a few million years.
The Galilean moon flybys
- GanymedeJuno flew past Ganymede in June 2021 and mapped its ice.
- EuropaIt passed Europa in September 2022, looking for ocean clues.
- IoClose passes in 2023 and 2024 watched Io’s volcanoes.
- OceansThese flybys probe water hidden under icy crusts.
- RelevanceWater beyond Earth shapes where life might start.
PYQ
Previous Year Questions
2017 Mains — GS Paper I
- PYQUPSC CSM 2017 GS Paper I, Q5 — View this question
- AskThe question wants Juno’s contribution to Earth’s origin story.
- PlanExplain Juno’s water, core and formation-model findings first.
- TipLink Jupiter’s story to Earth’s water and the early solar system.
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