EPSC Abstracts Vol. 9, EPSC2014-229, 2014 European Planetary Science Congress 2014 EEuropeaPn PlanetarSy Science CCongress c Author(s) 2014
SUDA: A Dust Mass Spectrometer for Compositional Surface Mapping for a Mission to Europa
S. Kempf (1), N. Altobelli (2), C. Briois (3), E. Grün (1), M. Horanyi (1), F. Postberg (4), J. Schmidt (5), R. Srama (4), Z. Sternovsky (1), G. Tobie (6), and M. Zolotov (7) (1) LASP, University of Colorado at Boulder, Boulder, USA ([email protected]), (2) ESA, ESAC, Spain, (3) LPC2E, Orleans, France, (4) IRS, Stuttgart University, Stuttgart, Germany, (5) University of Oulu, Finland, (6) LPGN, Nantes, France, (7) Arizona State University, Tempe, USA
Abstract micrometeoroid impact on a Jovian moon produces a large number of ejecta particles whith a total mass on We developed a dust mass spectrometer to measure the the order of a few thousand times of that of the im- composition of ballistic dust particles populating the pactor [2]. These ejecta particles move on ballistic tra- thin exospheres that were detected around each of the jectories and most of them re-collide with the satellite Galilean moons. Since these grains are direct samples due to the lower initial speed. As a consequence, an from the moons’ icy surfaces, unique composition data almost isotropic dust exosphere is present around the will be obtained that will help to define and constrain moon [3, 7]. the geological activities on and below the moons? sur- In 1999, the Galileo dust instrument measured the face. The proposed instrument will make a vital con- density profiles of the tenuous dust exospheres around tribution to NASA’s planned Europa Clipper mission the Galilean satellites Callisto, Ganymede, and Europa and provide key answers to its main scientific ques- [4]. The cloud density decreases asymptotically with 5/2 tions about the surface composition, habitability, the radial distance as r− , i.e. the cloud extent is only icy crust, and exchange processes with the deeper in- of a few moon radii. However, a spacecraft during a terior of the Jovian icy moon Europa. close flyby at Europa will detect a substantial number The SUrface Dust Aanalyser (SUDA) is a time-of- of ejecta particles. The initial speed of most ejecta par- flight, reflectron-type impact mass spectrometer, opti- ticles is smaller than the escape velocity, which in turn mised for a high mass resolution which only weakly is much smaller than the speed of an orbiting space- depends on the impact location. The small size (268 craft. The ejecta particles thus hit the dust detector × 250 171 mm3), low mass (< 4 kg) and large sensitive with the velocity of the spacecraft and arrive from the × area (220 cm2) makes the instrument well suited for apex direction. The dynamic properties of the parti- the challenging demands of the Europa Clipper mis- cles forming the ejecta cloud are unique and can be sion. A full-size prototype SUDA instrument was built clearly distinguished from any other kind of cosmic in order to demonstrate its performance through cali- dust likely to be detected in the vicinity of the satel- bration experiments at the dust accelerator at NASA’s lite. IMPACT institute at Boulder, CO with a variety of cos- mochemically relevant dust analogues. The effective 2. Instrument description mass resolution of m/∆m of 200-250 is achieved for mass range of interest m = 1-250. The SUrface Dust Analyser (SUDA) is a reflectron- type, time-of-flight impact mass spectrometer, which 1. Dust Exoclouds has heritage from the Cassini CDA and the Stardust CIDA instruments. The main challenge for the design The basic idea of compositional mapping [1, 6] is that of a dust mass spectro-meter is to achieve simultane- moons without an atmosphere are ensgulfed in clouds ously a high mass resolution, a sufficiently large sensi- of dust particles released from their surfaces by mete- tive area, and a compact design. The plasma ions pro- oroid bombardment. The ejecta cloud particles can be duced by the hypervelocity impact may have a broad detected and their composition analyzed from orbit or energy distributions of up to 100 eV, which limits the during a spacecraft flyby. The ejecta pro-duction pro- mass resolution of linear TOF dust spectrometer of 8 cess is very efficient: a typical interplanetary 10− kg reasonable size to about m/∆m = 50. The effect of Ejecta Particle K 39 H Pt-coated Pyroxene Na Mg 23 24 Al Si Ag Ag 27 28 109 107 Mg Mg 26 Entrance Dust Time of Flight 25
Grid Signal Si Si 2 C 29 30 O
Dust Charge 12 Ca 40 K 41 9
H 22 24 26 28 30 32 34 4 2 C H
Reflectron Grid log Amplitude Ag
Impact Charge Fe AgMg AgMg 109 Ions Acceleration 56 109 107 2 2 Li Ag 7 CH Fe 107
Ag) Ag) Reflecting Grid Signal 3 56 H 109 Fe 107 ( ( E field 56 27T18:28:46
+3000V − MPI (c) 50 1002010−05−19T14:50:31 150 200 Ion Charge Mass (u) Acceleration Grid Ion Grid Signal H PPy-PMPV latex Na 23 Na 23
Target K C Accelerating 39 H 12 3 HCS? Ca 2 C 2
2010−139/15:07:04 40 3 E field 2 H 2 2 3 3 H H H 4 H 2 2 S/O 2 C H C C K 4 4 H C C C 32 K 3 5 2 C +2500V / 41 C 4 H 39 H C 4 2 S C C C -2500V Ion Sensor 34 2 H 3 H log Amplitude HCS?
TOF Signal C 25 30 35 40 45 50 30T20:42:44
2 4 6 8 10 12 5 log Amplitude 3 Time (µs) CH C C S/O H 32 4 2
Time C H 7 H 6 CH 5 C Au 4 C C
7 197 C 3 6 C H C 28T07:25:25