Juno: Changing Views of Solar System Formation Paul G. Steffes Professor and Associate Chair School of ECE, Georgia Institute of Technology With much assistance from Prof. Fran Bagenal, Univ. of Colorado

Juno Juno Science Presentation Juno Site Visit – Use or disclosure of any of the information of this package is subject to the restrictions on the cover page. 2 Juno Science Objectives Origin Determine O/H ratio (water abundance) and constrain core mass to decide among alternative theories of origin. Interior Understand Jupiter's interior structure and dynamical properties by mapping its gravitational and magnetic fields Atmosphere Map variations in atmospheric composition, temperature, cloud opacity and dynamics to depths greater than 100 bars at all latitudes. Magnetosphere Characterize and explore the three-dimensional structure of Jupiter's polar magnetosphere and auroras.

Juno Juno Science Presentation Juno Site Visit – Use or disclosure of any of the information of this package is subject to the restrictions on the cover page. 3 Juno Spacecraft & Payload Spacecraft 976kg (dry) Built around radiation vault Solar power - 2m x 7.5m arrays, ~300 W Spacecraft - sun-pointed 3rpm spinner Operations - simple and repetitive 15 kbps downlink Payload Gravity Science (JPL) Magnetometer— MAG (GSFC/JPL) Microwave Radiometer— MWR (JPL) Energetic Particle Detector—EPD (APL) Jovian Auroral Distributions Experiment— JADE (SwRI) Waves (U of Iowa) UV Spectrometer— UVS (SwRI) Visible Camera - JunoCam (Malin)

Juno Juno Science Presentation Juno Site Visit – Use or disclosure of any of the information of this package is subject to the restrictions on the cover page. 4 Public Engagement and Students “Giant Planet Story is the story of the solar system” Jupiter’s mysteries captivate public interest E/PO effort targets unique customer needs and involves students directly in science Students analyze the first images of Jupiter’s poles. No, it's not student-built….

Juno Juno Science Presentation Juno Site Visit – Use or disclosure of any of the information of this package is subject to the restrictions on the cover page. 5 Juno Mission Design Currently in Phase B Launch: August year cruise Baseline mission: 32 polar orbits Perijove ~5000 km 11 day period Spinner Solar-powered Science Objectives: Origin of Jupiter Interior Structure Atmosphere Composition & Dynamics Polar Magnetosphere

Juno Juno Science Presentation Juno Site Visit – Use or disclosure of any of the information of this package is subject to the restrictions on the cover page. 6 The History of the Solar System Present theories of solar system origin and evolution do not explain how Jupiter was enriched in heavy elements. This is key to understanding how giant planets form, in our own and other planetary systems. These heavy elements are the seeds for the Earth and life Jupiter’s formation – How, when, where, and how long?

Juno Juno Science Presentation Juno Site Visit – Use or disclosure of any of the information of this package is subject to the restrictions on the cover page. 7 Galileo Probe Results Galileo results show similar enrichment in key elements, independent of volatility Results imply Jupiter formed colder and/or further out than 5 AU Solid material that enriched Jupiter was most abundant solid material in early solar system Galileo probe abundances challenge planet formation models

8 Collapse of the Solar Nebula

9 H 2 O, NH 3, CH 4 W ater, A mmonia, M ethane Hydrogen compounds (in Jupiter) Ignore inert gases He, Ne, Ar

10  Abundant ice (H 2 O) condense beyond frost line  Snowballs -> bigger snowballs--> rock-ice planetary cores  Cores have enough gravity to hold H - most abundant element - > giant planets  Small amounts of rock & metal-> terrestrial planets

Formation of Jupiter and Origin of atmosphere Core accretion model Core from grains of ice, rock, metal Core from grains of ice, rock, metal Core grows to critical mass (poorly understood,~10 M E ) Core grows to critical mass (poorly understood,~10 M E ) Gravitational collapse: H 2, He (most volatile gases) captured Gravitational collapse: H 2, He (most volatile gases) captured Atmosphere from H 2, He; and volatiles from core Atmosphere from H 2, He; and volatiles from core Planetesimals added throughout the formation (and afterward) to explain heavy element enrichment Planetesimals added throughout the formation (and afterward) to explain heavy element enrichment Cold icy planetesimals Cold icy planetesimals Clathrate hydrates (stuff bonded in ice) Clathrate hydrates (stuff bonded in ice)

Jupiter clouds Equilibrium (expected) Hot Spot (Galileo observed)

Galileo Probe Gas Mass Spectrometer

889 nm (0.5 bar) 727 nm (3 bar) 756 nm (>3 bar) Galileo Imaging Gierasch, et al; Ingersoll, et al (2000) lightning winds

Elemental abundances at Jupiter (Galileo Probe Mass Spectrometer, GPMS)

 30 au 5 au evaporate + scatter  30K 150K Interstellar (ISM)  30K KBOs  30K Cold planetesimals and heavy element enrichment Requires T  30 K to trap N 2 and Ar 2-4  solar H 2 O

Origin: clathrate-hydrates Cold planetesimals from interstellar cloud may not have survived the formation of solar nebula (high T) Clathrate hydrates trap volatiles containing heavy elements in the cooling, feeding zone of Jupiter Clathrate hydrates trap volatiles containing heavy elements in the cooling, feeding zone of Jupiter Predicts 9  solar H 2 O, with 100% efficiency Predicts 9  solar H 2 O, with 100% efficiency of trapping in clathrates (Gautier et al., 2001)

What is missing? abundance in “well-mixed” atmosphere H 2 O is presumably the original carrier of heavy elements to Jupiter. Help is on the way! Juno Water

19 What water tells us!

Juno Juno Science Presentation Juno Site Visit – Use or disclosure of any of the information of this package is subject to the restrictions on the cover page. 20 Jupiter’s Atmosphere Water is likely carrier of heavy elements to the solar system Galileo was unable to determine global water abundance The source of the belt-zone structure unknown Jupiter’s atmosphere can tell us where and when?

Juno Juno Science Presentation Juno Site Visit – Use or disclosure of any of the information of this package is subject to the restrictions on the cover page. 21 Microwave Radiometry Radiometry sounds atmosphere to 1000 bar depth Determines water and ammonia global abundances 6 wavelengths between 1.3 and 50 cm

Juno Juno Science Presentation Juno Site Visit – Use or disclosure of any of the information of this package is subject to the restrictions on the cover page. 22 Microwave Radiometry 2 Global coverage ensures accurate measurement Observations investigate roots of belt-zone structure Builds on Earth (TOPEX, MISR, JASON) and Astrophysics (COBE) missions

Juno Juno Science Presentation Juno Site Visit – Use or disclosure of any of the information of this package is subject to the restrictions on the cover page. 23 Microwave Radiometry from 0.5 to >100 Bars Short wave channels sample NH 3 cloud Long wave channels sample H 2 O cloud and below Gives 3D coverage - latitude, emission angle, wavelength Water is crucial for origin of solar system and meteorology

Juno How Did We Get this Up Here? 544 kg (1200 lbs) += 726 kg (1600 lbs) 136 kg (300 lbs) Measurement System Sensitivity Study Summary

Juno How Does it all fit together? Measurement System Sensitivity Study Summary

Juno Let's go!