MAVEN OBSERVATIONS OF SIDING SPRING AND MARS. Roger Yelle and MAVEN Team

Transcription

1 MAVEN OBSERVATIONS OF SIDING SPRING AND MARS Roger Yelle and MAVEN Team APP/CSS Mee=ng, 11 August 2014

2 Some Per=nent Facts The closest approach occurs on 19 Oct 2014, at 18:28 UT at a distance of 136,000 km. The Mars- Comet rela=ve velocity is 56 km/s, corresponding to an energy of 300 ev for H 2 O. The neutral coma extends over 100,000 km. The H coma extends ~1,000,000 km. The bow shock distance is unknown, but could be tens of thousands of kilometers. The =me scale for energy/mass deposi=on into the atmosphere is ~1 hour. APP/CSS Mee=ng, 11 August 2014

3 MAVEN INSTRUMENTS NGIMS: Ion- Neutral Mass Spectrometer IUVS: UV Imaging Spectrograph LPW/EUV: Langmuir Probe, EUV monitor STATIC: Thermal and Suprathermal Ion Analyzer SEP: Solar Energe=c Par=cle (electrons & Ions) SWEA: Electron Spectrometer SWIA: Solar Wind Ion Analyzer MAG: Magnetometer APP/CSS Mee=ng, 11 August 2014

4 Comet Neutral Gas Environment: Model Q(H 2 O) = 5 x s - 1 for 67P/C- G at 1.3 AU 5% CO, 5% CO 2 (Tenishev et al. 2008) (m - 3 ) km = CO 2? (m) APP/CSS Mee=ng, 11 August 2014

5 Ion Tail Geometry and Simple Model An-- Sun Direc-on Path of Mars in comet frame APP/CSS Mee=ng, 11 August 2014

6 MAVEN PLAN First UV Observa=ons at - 5 days Extensive Observa=ons at - 2 days Mars Science Observa=ons Start Early at - 1 day, all instruments deployed and opera=ng. Spacecraf in safe mode for ~2 orbits centered on max dust peak (+98 min afer CA). Science Observa=ons Resume for ~2 days Spacecraf checkout resumes. MAG/LPW/SEP operate con=nuously. APP/CSS Mee=ng, 11 August 2014

7 Geometry Comet Input at - 8 deg La=tude, 6 AM, E Longitude MAVEN Periapse, +44 deg La=tude, 2:30 PM 2 passes afer hiding, Longitude, E Longitude, quite close to max comet input loca=on. APP/CSS Mee=ng, 11 August 2014

8 We have been alloked 5 orbits to image the comet For a small frac=on of this =me Mars is obscuring the comet Afer the comet imaging, we immediately begin Mars science imaging with 4x data rate Observa=on Cycle

9 Science: Comet Observa=ons Interac=on of the comet coma with the solar wind produces energe=c ions and electrons that should be detectable with SEP, SWIA, SWEA, and STATIC. The solar wind will be perturbed by the comet interac=on, producing signatures observable by all MAVEN instruments that measure the solar wind (SEP, SWIA, SWEA, STATIC, MAG). UV emissions from the coma can be mapped with excep=onally high spa=al resolu=on. LPW may detect small comet grains. These observa=ons are possible even for a weak comet. APP/CSS Mee=ng, 11 August 2014

10 Brightness By Species 1 Slit Width on Oct 18th 1 Slit Width on Oct 17th 1 Degree on Oct 18th 5 Degrees on Oct 18th 1 Degree on Oct 17th 5 Degrees on Oct 17t

11 UV Observa=on Modes Echelle: Primary target is D/H, some O lines may be present. Near Nucleus Faint Emissions: 2x2 degree imaging of the nucleus at 60 sec Near Nucleus Bright Emissions: 2x2 degree imaging of the nucleus at 6 sec LyA and OH Coma: 10x10 degree imaging of the nucleus at 60 sec Background: Full sweep across both FORs

12 LyA and OH Coma:

13 Bright Features:

14 Bright Features:

15 Faint Features:

16 Faint Features:

17 IUVS Echelle D/H Measurement Owen et al. (1999) APP/CSS Mee=ng, 11 August 2014

18 APP/CSS Mee=ng, 11 August 2014 Ali et al. (2014)

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21 Ion cyclotron waves from Siding Spring Produced by ionized H 2 O from the comet Sensi=ve measure of comet s neutral gas environment Waves could be observed by MAG from ±4.9 hrs from closest approach Assuming threshold of 0.1 nt amplitude and an H 2 O produc=on rate of 2x10 28 s - 1 Equivalent to a column of 1.5x10 12 H 2 O- m - 2, 20 m - 3 pickup ion density or 1.2x10 6 km from closest approach to the comet Constrains neutral input into mar=an atmosphere APP/CSS Mee=ng, 11 August 2014 Crary et al. in prepara=on

22 Mars Observa=ons Direct comet input causes: Thermal/CO 2 density perturba=ons. Circula=on pakern perturba=ons. Changes in neutral composi=on: H, D, others? Changes in Ion composi=on: H/D- bearing ions, others? Thermal and suprathermal electron distribu=on perturba=ons. All proper=es of the induced magnetosphere Alkali and metallic ions in the middle atmosphere Indirect Effects Perturba=on of solar wind alters Mars Solar wind interac=on affec=ng energe=c ion and electron distribu=ons and input to atmosphere. APP/CSS Mee=ng, 11 August 2014

23 SIDING- SPRING APP/CSS Mee=ng, 11 August 2014

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25 APP/CSS Mee=ng, 11 August 2014 Yelle et al. (2014)

26 APP/CSS Mee=ng, 11 August 2014 Yelle et al. (2014)

27 APP/CSS Mee=ng, 11 August 2014 Maka et al. (2014) submiked

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30 H Escape During Encounter Escaping Atoms APP/CSS Mee=ng, 11 August 2014

31 Summary MAVEN will observe Siding Spring (assuming MOI goes smoothly) Extensive UV mapping of coma Fields and Par=cle measurements of solar wind interac=on Possible dust detec=on Substan=al perturba=ons of Upper Atmosphere expected for large enough Q (~> 1E28 s^- 1). MAVEN will observe Mars Opera=on in standard science mode, to measure densi=es, temperature, UV emissions, ionosphere, and escape rates. APP/CSS Mee=ng, 11 August 2014