Jupiter descent · Mission profileSheet 00 · Approach
Atmospheric entry and descent · profile sheet

Jupiter
descent

From the cloud tops to the centre of the largest planet: 71,492 km straight down. One probe has ever gone in. This page follows it, and then keeps going.

Solid lines and numbers were measured on the way down. Dashed and hatched means worked out from outside. Nothing has been there. The marbled background: colour is the layer you are in, drift is the wind.

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How to read this sheet
Solid lines and numbers were measured on the way down. Dashed and hatched means worked out from outside. Nothing has been there. The marbled background: colour is the layer you are in, drift is the wind.
ApproachSeen from outside

A planet with no ground

Jupiter is 11 Earths wide and 318 Earths heavy, and it is almost all hydrogen and helium, the same stuff as the Sun. The stripes are cloud bands, each one a jet stream blowing the opposite way to its neighbours. The whole planet spins once in under 10 hours.

Target · 6.5° northMeasured in place

One probe, one hour

On 7 December 1995 NASA's Galileo spacecraft dropped a 339 kg probe into the clouds just north of the equator. It sent back 58 minutes of readings. Those are still the only measurements ever made inside a giant planet.

Sheet 10 · How hotTemperature on the way down

Read it top to bottom, like the descent. Each step down the left side is ten times more pressure. The line is solid where the probe measured it and dashed where it comes from models.

Both scales are squeezed (logarithmic) so that the clouds and the core fit on one sheet. Point or tap for values.

Sheet 11 · True scaleHow far the probe got

The whole way to the centre, drawn to scale. The probe's 58 minutes covered 0.19% of it. If Jupiter were an apple, the probe did not get through the skin.

    The layers have no sharp edges, so the colours blend where one turns into the next. Depths below 133 km are from models.

    Sheet 12 · The numbersStops on the way

    NotesWhat is simplified

    • Depth zero is the 1-bar level, the usual convention, because there is no ground. "Cloud tops" are 20 to 50 km above it. The total of 71,492 km is the equatorial radius; the planet is 7% shorter pole to pole.
    • The probe's site was unusual. It fell into a dry clearing, so its cloud and water readings are not typical. Cloud-deck pressures here are the textbook ranges (0.6 to 0.9, 1 to 2, 3 to 7 bar), which vary from place to place.
    • Below 22 bar nothing is measured. Temperatures follow published models (about 5,000 to 8,400 °C where hydrogen turns metallic, about 20,000 °C at the centre). Pressures at depth use the simplest textbook model of a gas giant, which lands inside the spread of published ones. Teams still disagree by tens of percent.
    • "About 3,000 km" for the winds is one reading of Juno's gravity data. Other wind patterns can fit the same data.
    • The fate of the probe below its last signal is an estimate: NASA's figure is that it was destroyed by about 1,700 °C and 5,000 bar. The melting-point markers are those temperatures placed on the model.
    • The core is drawn as speckles thinning outward because that is the current best idea, not a picture of anything seen. Estimates of its size run from 30% to 60% of the radius.
    • The background is not a view. At these temperatures the deep interior would glow white-hot and be opaque. The marbling is a diagram: its colour marks the layer and its motion follows the wind. Wind is shown blowing one way because the probe sat in a single jet.
    • What colours the clouds red and brown is not known. The palette is from Juno's camera images.

    ReferencesSources

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