Galaxy Forum USA 2016 - Prof Imke de Pater, UC Berkeley

Imke de Pater (UC Berkeley)

Outline

• Jupiter: the planet

• Why study Jupiter? Origin of our Solar System• Recent work by our group• The Juno Mission

HST/NASA

• Largest planet in our SS• ~12 x larger than Earth• ~300 times more mass• ~85% H2, 15% He• trace amounts CH4, NH3,

H2O, H2S (on Sun: C,N,O,S)

Cassini, Oct. 31 – Nov. 9, 2000

HST/NASA

Cassini, Oct. 31 – Nov. 9, 2000

HST/NASA

So, Why study Jupiter?

• Composition and internal structure Jupiter à

information on conditions of our solar nebula during the time the Sun and

planets formed.

Fundamental Question: How did our Solar System Form?

Composition of a planet can be determined through remote sensing or in situ (probe)

IRTF

VLA

50 0 -50

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Jovic

entri

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System III Longitudeo o o

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Visible (HST) 5 µm (IRTF) 2 cm (VLA)

1995-‐1996: Galileo Probe entry

Determine composition through observations at different wavelengths

Beebe Ortiz et al., 1998 de Pater et al. 2001

IRTF

VLA

50 0 -50

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Jovic

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System III Longitudeo o o

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Visible (HST) 5 µm (IRTF) 2 cm (VLA)

1995-‐1996: Galileo Probe entry

Radio: clouds are transparant; Most of the opacity is caused by NH3 gas. At longer wavelengths radiation is received from deeper levels in the atmosphere. à NH3abundance very similar to solar N value.

Beebe Ortiz et al., 1998 de Pater et al. 2001

Two questions surface: • What is the H2O abundance in Jupiter’s deep atmosphere?• How to reconcile the groundbased (radio) measurement

of NH3 with the Galileo Probe data?

Owen et al. 1999

How can we “loose” NH3 gas between 4 and 8 bar?

• Chemistry; perhaps H2S binds with more than 1 NH3molecules? Or the water cloud takes up more NH3 than hitherto assumed? Lab work ongoing

• Dynamics: updrafts, downdrafts, drying out air, as the zone-‐belt generic picture.

10–16 10–14 10–12 10–10 10–8

Cloud density rate Rx (g cm–3 cm–1)

300

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Tem

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(K)

7.0

5.04.0

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Pres

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(bar

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Water solution

Water ice

NH4SH solid

NH3 ice

Wong et al., 2014

In order to solve the NH3 and H2O questions, we obtained data to probe below Jupiter’s clouds:

• Spectroscopic data at 5 µm• Maps at radio wavelengths at 2-‐6 cm (4-‐18 GHz)

De Pater et al., 2011

5-‐µm image of Jupiter’s northern hemisphere.

In hot regions (hot spots, 5-‐µm rings around vortices) we probe down to 5-‐7 bar

Bjoraker et al., 2015

Zones exhibit narrow CH3D line profiles. Modeling indicates the presence of a cloud at ~4 bars, which must be a water cloud.à Consistent with historical picture of rising air in zones, sinking in belts; H2O must be >1.2 x solar O.

Hot Spots, Belts, and high-‐latitude regions exhibit broad CH3D line profiles àprobing ~7 bar àNo opaque H2O

clouds.

5-‐µm Spectra

de Pater et al., 2016

Radio observations at 2 -‐ 6 cm (or 4 – 18 GHz)

NH3

SolutionH2O

NH4SH

Equilibrium NH3(Fig. 3A, profile a)

Depleted NH3(Fig. 3A, profile e)

17.4 GHz

4.42 GHz7.45 GHz11.5 GHz14.2 GHz

1.46 GHz

17.4 GHz

4.42 GHz7.45 GHz11.5 GHz14.2 GHz

1.46 GHz

A B

Fig. 1

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Normalized contribution functions

Pres

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Temperature (K)

0 0.5 1 1.5

100 200 300 400

Normalized contribution functions

Temperature (K)

JUPITER:Radio spectrum

Temperature (K)

De Pater et al., 2016

NH4SH àNH3-‐ice à

brg c

Temperature (K)

TP profile



2 cm

2 cm

6 cm

3.5 cm


SUMMARY:

• Microwave maps show spatial variations in Tb, resembling

visible light maps.

• Radio-‐hot belt at ~8 deg N

• Localized NH3 depletions (hot spots) down to > 8 bar

• Localized upwellings (plumes) from P > 8 bar: planetary wave, connecting the 5-‐µm hot spots and plumes.

• Plumes explain radio – Galileo conundrum

NASA’s Juno Mission• Launch Aug 5th 2011.• Arrival July 4th 2016 • 2700 miles above the jovian

cloud tops in a polar orbit• Key goals:

– Gravity field mapping to detect the presence of a core.

– Microwave mapping to peer beneath the clouds, constrain oxygen.

• 32 orbits: 1-‐8 for remote sensing and microwave.

• 9-‐32 for gravity mapping• De-‐orbit March 2018.

Slide adapted from Orton

26

Juno’s Specific Science ObjectivesOrigin

Determine water abundance and constrain core mass to decide among alternative theories of origin.

InteriorUnderstand Jupiter's interior structure and dynamical properties by mapping its gravitational and magnetic fields

AtmosphereMap variations in atmospheric composition, cloud opacity and dynamics to depths greater than 100 bars at all latitudes.

MagnetosphereCharacterize the three-‐dimensional structure of Jupiter's polar magnetosphere and auroras.


Probing the deep interior from orbit

Juno maps Jupiter from the deepest interior to the atmosphere using microwaves, and magnetic and gravity fields.


Mapping Jupiter’s gravityTracking changes in Juno’s velocity reveals Jupiter’s gravity (and how the planet is arranged on the inside).

Precise Doppler measurements of spacecraft motion reveal the gravity field.


Juno’s Microwave Radiometer measures thermal radiation from the atmosphere to as deep as a few 100 bar pressure (few 100 km below the visible cloud tops).

Sensing the deep atmosphere

Goal: to determine the 3D H2O and NH3 abundances.

Sensing the deep atmosphere

At wavelengths > 6 cm (freqs < 4 GHz) Jupiter’s synchrotron radiation makes it very difficult to map the atmosphere from the Earth. Juno flies inside the radiation belts. VLA map at 21 cm;


Juno’s field of view is tiny à need context maps.

Slide adapted from Bagenal

Mapping Jupiter’s magnetic field and aurora

HST/NASA

Ground-‐based observing campaign to support Juno

• Dedicated network of amateur astronomers.

• Many telescopes allocated time, from X-‐rays to uv-‐visible, near-‐and mid-‐infrared, and radio from cm—m wavelengths.

• Unique opportunity to characterize Jupiter’s atmosphere from the stratosphere down to 100’s of bars. Time variability mandates simultaneous data to fully characterize the planet.

• Synergy VLA & Juno: VLA provides context maps to put Juno MWR data in perspective; Juno extends the information to much deeper levels. Juno also has a superb view of the poles.