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Solar-system observations with Herschel/ALMA

Solar-system observations with Herschel/ALMA. T. Encrenaz, D. Bockelée-Morvan, J. Crovisier, E. Lellouch LESIA, Observatoire de Paris. Outline. Why the far-IR/submm/mm range? Major objectives of solar-system research Venus, Mars and the giant planets Satellites, distant asteroids and TNOs

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Solar-system observations with Herschel/ALMA

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  1. Solar-system observations with Herschel/ALMA T. Encrenaz, D. Bockelée-Morvan, J. Crovisier, E. Lellouch LESIA, Observatoire de Paris

  2. Outline • Why the far-IR/submm/mm range? • Major objectives of solar-system research • Venus, Mars and the giant planets • Satellites, distant asteroids and TNOs • Comets

  3. Why the far-IR/submm/mm range? • Solar-system objects are COLD objects which radiate at low frequencies • Strong molecular rotational transitions • Ideal for: • planetary atmospheres • cometary atmospheres • distant objects (TNOs)

  4. Many major discoveries in planetary and cometary science • First detection of HCN in Comet Halley (1986) • Over 20 parent molecules detected in Hale-Bopp (1997) • First detection of a stable atmosphere (SO2) around Io (1990); also SO and NaCl(2002) • Detection of new molecules in Jupiter after the SL9 collision (1994):CO, CS, OCS, HCN • First detection of H2O2 on Mars (2004)

  5. Major issues in solar-system sciences • Origin of the solar system: • Giant planets ’ composition: D/H, He/H, oxygen source • Comets ’ composition and link with ISM: minor constituents, D/H in various species • TNOs: Ts/albedo • Evolution of solar-system objects • Minor constituents and dynamics of planetary and satellite atmospheres • Comets ’ activity, physico-chemistry and thermodynamics

  6. Venus • CO, H2O/HDO observed in the mm range -> vertical distributions + wind measurements • No observation with ISO nor Herschel • Perspective with ALMA: • velocity field from CO, H2O, H218O maps (-> D/H) • dynamics of the mesosphere (z = 100 km): zonal super-rotation, global circulation • Search for minor mesospheric species (HCl, H2S, SO2) • Follow-up of Venus Express

  7. Mars: a prime objective of planetary exploration • Questions: • Past and present climate • Water cycle • Evidence for liquid water in the past? • Evidence for traces of fossil life? • An extensive space exploration with orbiters and landers (« Follow the water »)

  8. Mars:High-resolution spectroscopy • CO, H2O/HDO/H218O observed in the mm range -> vertical distributions • ISO, Odin, SWAS -> water distribution • Perspectives with Herschel and ALMA: • H2O, CO and isotopes (in part. D/H) • Minor species: H2O2, O2, O3 • Search for undetected species: HCl, NH3, HO2, H2CO, SO2, H2S, OCS…

  9. MARS: OBSERVATIONS WITH ODIN Biver et al., 2004

  10. Ozone on Mars with Herschel

  11. NH3 on Mars with Herschel and ALMA (Q= 5 10-10) Herschel ALMA

  12. Mars: A 3-D dynamical picture of the middle atmosphere(winds, T(P) and water mapping) • First maps using CO(2-1) at IRAM (30m & PdB) • Comparison with GCM: good overall agreement but strong retrograde winds observed whatever the season • -> future observations important for better understanding the martian climate • -> Major objective for ALMA • Complementarity with space missions (Mars Express and future orbiters )

  13. Mars velocity field, IRAM PdB (Moreno, 2001) z = 50 -70 km Perspectives with ALMA: DV = 3-5 m/s, spatial resolution on Mars: about 100 km

  14. Giant planets: formation • D/H: a tracer of giant planets ’ formation • In Jupiter and Saturn (mostly made of protosolar gas): reflects the protosolar value • In Uranus and Neptune ( mostly made of an icy core): enriched vs protosolar value • Expected: • (D/H)PS=(D/H)J <(D/H)S<(D/H)U,N<(D/H)C • Confirmed by ISO & Galileo measurements

  15. HD: ISO/SWS Feuchtgruber et al., 1999 Lellouch et al., 2001 Deuterium in the Solar System

  16. What to do with Herschel? • New measurement of HD at 56 and 112 mm on the four giant planets with PACS • Questions: • Is (D/H)S > (D/H)J ? • Are (D/H) in protoneptunian ices different from cometary values? • Is D/H in Oort-cloud comets the same as in Kuiper-Belt comets?

  17. Giant planets: evolution • He/H: a tracer of giant planets ’ evolution • In Jupiter and (even more) in Saturn: He is expected to be depleted vs the protosolar value due to condensation in liquid hydrogen during the cooling phase • In Uranus and Neptune: • no liquid hydrogen expected • but H partly linked in ices • -> He/H might be enriched in the gas phase • Present determination are still uncertain (except Jupiter) • Future: Cassini CIRS (Saturn), Herschel/PACS (Uranus,Neptune), from the far-IR continuum

  18. He/H in the giant planets Jupiter: Galileo mass spectrometer Saturn, Uranus, Neptune: Voyager (IRIS)

  19. The oxygen source in the giant planets and Titan • H2O and CO2 emissions detected by ISO-SWS + SWAS/ODIN (Jupiter, Saturn) • Comparable H2O input fluxes: 105-107 cm-2 s-1 • Possible sources: • interplanetary flux (U, N), • local source (rings, satellites)(S, T?), • cometary impacts (J?) • Important implications on: • Dust production and water content at large Rh (collisions in the Kuiper Belt?) • Rate of cometary impacts

  20. Observation of the H2O vertical distribution in Jupiter with SWAS Bergin et al. 2000

  21. Oxygen source: What to do with Herschel and ALMA?NB: For Saturn: complementarity Herschel/Cassini-CIRS • Herschel: • H2O abundance and variability • Possible role of cometary impacts • H2O vertical distribution (HIFI) • Constrains on transport models • Low-resolution mapping of J and S (PACS) • Possible trapping in aurorae • ALMA: HDO high-resolution mapping • Determination of D/H in external source?

  22. Why are Uranus and Neptune so different? • Strong internal source in Neptune, not in Uranus • CO and HCN abundant in Neptune ’s stratosphere (CON = 10-6, COU = 3 10-8) • CO mostly internal in Neptune, probably external in Uranus • Uranus is much more sluggish (eddy diffusion coefficient 103 times less than in Neptune)

  23. What to do with Herschel and ALMA? • Search for tropospheric CO and PH3 (tracer of vertical motions in Jupiter and Saturn ’s tropospheres) • PH3 expected to be abundant in Neptune, apparently absent in Uranus (convection inhibited?) • Search for CH4 emission lines • oversaturation observed in Neptune, not in Uranus • Search for photochemical products in Neptune (nitriles)

  24. Detectability of stratospheric CH4 in Uranus and Neptune with Herschel/PACS

  25. Satellites & Pluto with ALMA • Io • Search for minor species (H2S, S2O, KCl, SiO…) • SO2 low-res. Mapping (-> volcanism monitoring) • Titan (complementarity with Cassini/CIRS) • Mapping of CH3CN, HC3N at z = 500 km -> dynamics, photochemistry • HCN: winds (low-res.map), D/H • Triton and Pluto • Search for CO, HCN…

  26. Distant asteroids and TNOs • Interest of far-IR/submm measurements: determination of diameter + Ts (in the visible: aD2 is measured) • Spitzer program (GTO): 114 TNOs, 14 Centaurs • With Herschel: possible to reach D=300 km at 40 AU • With ALMA: 300 km at 80 UA

  27. HERSCHEL/SPIRE 250 micron Sensitivity (1  - 1h) = 0.6 mJy Detectability of TNOs with Herschel/SPIRE

  28. Observations of comets with Herschel and ALMA (1) • Water-rich objects ->Study with Herschel • Activity monitoring • D/H -> origin • Tinitial from ortho/para ratio -> origin • Tcoma from H2O line intensities -> thermodynamics • Doppler shifts -> velocity fields -> thermodynamics, study of jets...

  29. Observations of comets with Herschel and ALMA (2) • Many complex parent molecules -> study with ALMA • Search for new species (possible candidates: all ISM molecules!) • Chemical diversity among comets • Relative abundances -> link with ISM • Isotopic ratios (D/H in HCN, HNC, H2CO…) -> link with ISM • Velocity fields -> thermodynamics, origin of outgassing (nucleus, grains), structure (jets)

  30. The heritage from ISO: high-resolution spectroscopy of rovibrational bands Crovisier et al., 1997

  31. The heritage from SWAS: the 557 GHz line in comet C 1999 H I (Lee) About 12 comets observed with SWAS and/or ODIN

  32. The heritage from ground-based observations: Evolution of production rates with heliocentric distances Biver et al., 2002

  33. Parent molecules observed in comets • In the far-IR/radio range: • H2O, CO, CH3OH, H2CO, HCN, H2S • NH3, HNCO,CH3CN,HNC, OCS (Hyakutake) • HCOOH, CH3CHO, HCOOCH3, NH2CHO, HC3N, H2CS, SO, SO2 (Hale-Bopp) • In the near-IR range: • H2O, CO, CO2, H2CO, OCS, saturated & unsaturated hydrocarbons • CH4, C2H2, C2H6, OCS, NH3 (Hyakutake, Hale-Bopp)

  34. Water in comets (Herschel) • H2O in a sample of weak comets (down to Q=1026 s-1)-> prod. rates (HIFI, 557 GHz) • H2O monitoring as a function of Rh (HIFI, 557 GHz) • Search for H2O in distant weakly active objects (link with asteroids) • Measurement of D/H in H2O

  35. D/H in comets • D/H in water: a stringent clue to the formation of comets (T, Rh) • D/H is known for only 3 Oort-cloud comets, not for Kuiper-belt comets • HDO lines will be searched for with HIFI for bright comets (Q > 2 1028 s-1) • D/H in other species (HCN, HNC…) will be searched for with ALMA

  36. A few good targets for Herschel • 8P/TuttleJanuary 2008, Q[H2O] = 3. 1028 s-1D = 0.25 AU • 46P/Wirtanen February 2008, Q[H2O] = 1. 1028 s-1 • 85P/Boethin December 2008, Q[H2O] = 3. 1028 s-1 • 67P/Churyu.-GDecember 2008, Q[H2O] = 5. 1027 s-1 • 22P/Kopff May 2009, Q[H2O] = 2.5 1028 s-1 • 81P/Wild 2February 2010, Q[H2O] = 1.3 1028 s-1 • 103P/Hartley 2October 2010, Q[H2O] = 1.2 1028 s-1D = 0.12 AU + possible brighter targets as Targets of Opportunity

  37. Mapping cometary atmospheres CO 230 GHz/Hale-Bopp with IRAM PdB ALMA Instantaneous 3-D maps of gaseous and dust (thermal) emissions Coma morphology, spiral gaseous jets, nucleus outgassing, rotation properties, dust/gas links Gas temperature and velocity maps Nucleus thermal emission on long baselines: size, albedo Henry,2003

  38. In summary... • Herschel/ALMA observations of solar-system objects will be precious in addition to space missions (MEx, VEx, Rosetta) • D/H in the solar system-> origins • Search for minor species in comets-> link with the ISM • Observation of many samples (KB comets, TNOs) • High-resolution mapping of planets and satellites • A major program with Herschel: H2O in the solar system • Formation of planets and comets • Activity of outer small bodies and water content in outer planetesimals

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