Maarten RoosSerote Obs' Astron' Lisbon

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Luisteren naar Mars Zoeken naar radiosporen van
stofduivels
Maarten Roos-Serote (Obs. Astron.
Lisbon) Daphne Stam and Rob Fender (UvA)
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Korte CV

• Sterrenkunde Leiden met afstudeeronderzoek in
  Paris aan Galileo/NIMS Venus atmosfeer (1993)
  wolken en temperatuur profiel.
• Promotie Galileo/NIMS/SSI Jupiter atmosfeer
  (1997) wolken en samenstelling.
• Nu (nog !) OAL Galileo/NIMS, Cassini/VIMS, Venus
  Express/VIRTIS, Centaur/TNO, Mars !

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Mars' Dust

• Background opacity ltlt 1, dust event opacity gtgt 1
• Influence meteorology and climat
• Size 2 - 4 micron.
• Composition Si-rich (e.g. feldspars), FexOy
• Optical Prop.
• w between 0.5 - 0.9
• g about 0.6
• Irregular (?)

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Mars' Dust Events
Local Regional Global feedback
feedback
Dust storm, North pole Spring.
Dust devils MOC WAC, red-filter image (18S,
85W, Biener, et al., 2002).
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Mars' Dust Events

• Local (dust devils) always and everywhere.
• Higher frequency in southern regions (e.g.
  Hellas) in the southern summer.
• Probability for a GLOBAL storm is about 33
  during any southern warm season.

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Mars' Dust Devils
Traces of aeolian processes are abundant !
(Malin et al. 1998)
MOC/NAC
MOC/WAC
Dust Devil Tracks
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Mars' Dust Devils

• Frequency
• Higher in sloped terrain large horizontal DT.
• During warm seasons.
• Structure
• Warm core vortices (convective heat engines)
• D p 50 Pa, D T 20 K (center - normal)
• Wind speeds 60 m/s (Renno et al. 2000)
• Lift dust particles small (- charge) go high

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Mars' Dust Devils
Dust Devils on Mars and on Earth
Mars Earth height
lt 7 km lt 0.1 km diameter lt 1 km
lt 0.01 km E_field gt 10 kV/m
100 kV/m E_break 5-20 kV/m 3000 kV/m
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Radio Emission from Mars

• 1960 1970, single dish observations
• Spectrum is flat (T ? 200 K) from 0.1 20 cm !
• Variation with longitude.
• Variation with time !
• 1980 1990, VLA observations (2-6 cm)
• T ? 193 K (whole disk average)
• Sub-surface
• Density about 1-2 g/cm3 (OK with in situ
  measurements)
• Di-electric constant about 2.5

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Radio Emission from Dust Events ?
Measured Martian disk radio brightness
temperatures as a function of the central
meridian longitude for 1975 (top) and 1978
(bottom) campaigns. The re-normalized brightness
temperature for 1975 is also shown in the bottom
plot (after Doherty et al., 1979). Some of the
most active dust devil/storm incubator regions
are marked in plot at the top.
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Radio Emission from Dust Events ?
Temperature of the Mars Orbiter Camera telescope
tube during a year of weak dust storm activity
(Year 1, 2000) and during a year of intense dust
storm activity (Year 2, 2001). The figure is a
courtesy of NASA/JPL/Malin Space Science Systems.
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Mars' Dust electricity

• Charging through collisional processes
  (tribo-electric processes) f(E,A,r,comp.,?).
• Particle-particle discharges (Renno et al. 2003)
• Mostly in saltation layer near the ground.
• Fraction of Mars covered by DD about 10-7.
• DDs produce broadband radio emission ?T ? 10-5
  K.
• In dust storms ?T can be up to 10 K.
• Radio emission
• Wavelengths gt 0.03 cm.
• Non-thermal.

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Our Idea new observations

• Systematic monitoring of Mars.
• Detect time variation in radio emission.
• Link to time variation in atmospheric dust
  content ?
• Use Radio and Visible / IR.
• Measure !!

? Pilot Study ?
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Westerbork SRT
29jul
10aug
23aug
03sep
15sep
Westerbork Synthesis Radio Telescope. 6 cm and 21
cm
27sep
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Westerbork SRT
Example at 6cm
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Nançay RT

• Nançay RT Transit Instrument.
• Observe 1 CM per day at 11 and 21 cm.

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Nançay RT
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Visible / IR
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Work in Progress

• Calibration of NRT data almost done
• Reduction and analysis of WSRT
• New observations with NRT and WSRT on Jan. 4
  2004, just after regional dust event !
• Lab. work.....can we simulate it in the lab ?