C OMPARING O BSERVATIONS OF THE A BUNDANCE OF S ODIUM IN M ERCURY S - PowerPoint PPT Presentation

C OMPARING O BSERVATIONS OF THE A BUNDANCE OF S ODIUM IN M ERCURY ’ S E XOSPHERE 1 Presenter: Alexander Lanzano Mentors: Aimee Merkel, Timothy Cassidy, Bill McClintock

M OTIVATION  Mercury is highly vulnerable to the Sun Its exosphere is most likely dependent on the amount of radiation the  planet receives  MESSENGER is one of the first satellites to obtain data about the exosphere from orbit  We can compare this new data to ground based data to see if there are any corresponding trends  Discovering how the exosphere is influenced by the Sun can give us an insight into: The chemical composition of Mercury  How the planet might have formed  How our Solar System might have formed  2 What other planets might be like in other system at similar distances as  Mercury is from the Sun

O UTLINE  Background on Mercury and the solar influence on its exosphere  Variables of interest  Observations from Earth  Observations from MESSENGER  Comparison of the two data sets  Observed trends 3

M ERCURY  General Facts  Smallest planet, 6% Earth  1 year = 88 Earth days Mercury  1 day = 176 Earth days  Highly eccentric orbit  Magnetic field present  Virtually no atmosphere  Highly influenced by the Sun  High energy particle collisions  Radiation pressure 4 Earth’s moon

M ERCURY ’ S A TMOSPHERE  No sustainable atmosphere  Thin Exosphere  H, He, O, Ca, Mg, K Na  Resembles comet tail  Source of Exosphere  Sputtering  PSD  Thermal Evaporation 5  Impact evaporation

Sprague et al. 1997 Photon Emission vs Spectrum Wavelength D ETERMINE S OLAR I NFLUENCE D2 BY V ARIATION IN OBSERVED N A D1 Counts  Search for increase in Na density:  D1 and D2 (yellow) spectrum 580 nm  How does it change with respect to: Wavelength (angstroms)  Time of Day  Change of season 6

G ROUND B ASED O BSERVATION M ETHOD y N N x S Observation Slit 7

S PRAGUE ET AL . O BSERVATIONS Sprague et al. 1997  Sprague et al.’s conclusions:  Na column density varies with local time  Did not account for True Anomaly 8

C OMPILING THE D ATA Sprague et al. 1997 9

D ETERMINE L OCAL T IME Sub-Solar Point Mercury X Sub-Earth Point 10 Y

Column Density (cm -2 ) 6:00-8:00 8:00-11:00 11:00-13:00 13:00-15:00 15:00-18:00 11 Local Time (hrs)

N EW P ARAMETERS OF I NTEREST  True Anomaly Used to determine seasonal variability of Na density  Mercury True Anomaly θ Closest Point to the Sun Sun 12

Column Density (cm -2 ) 13

T HE MESSENGER M ISSION  Takes vertical profile scans of Mercury’s exosphere  Uses UVVS  Records Na Column density for:  Local time  Seasonal variability  8 Mercury years of data (2 Earth years) 14

Column Density (cm -2 ) 15

C OMPETING F ACTORS  Sunlight Exposure vs Radiation Pressure  Greater photon intensity closer to the sunlight means more Na vaporization, but…  Being closer to the sun means more radiation pressure that disperses the exosphere Low Intensity Low Pressure True Anomaly=180 o High Intensity High Pressure True Anomaly= 0 o 16

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C ONCLUSIONS  Increases in Na density depends on:  True Anomaly  Local time  Both ground based and MESSENGER data are same order of magnitude  Overall: Data show similar trends! 23

F UTURE W ORK  Conduct an analysis of outliers in Sprague data  Attempt to account for difference in D1 an D2 spectra  Compare to other ground based data that used different observation techniques  Potter et al. 24

R EFERENCES AND IMAGES  Image slide 1: http://nssdc.gsfc.nasa.gov/image/spacecraft/messenger.jpg  Images slide 4: http://history.nasa.gov/EP-177/i2-6.jpg   http://www.8planets.co.uk/wp- content/themes/8planets/images/moon_surface_apollo_11_lg.jpg http://undsci.berkeley.edu/images/us101/mercury.gif   Image slide 5: http://www.windows2universe.org/mercury/Atmosphere/mercury_exosphere_ sodium_oct_2008_sm.jpg  Image slide 5: http://upload.wikimedia.org/wikipedia/commons/2/2f/Fraunhofer_lines.svg  Plot slide 5: Sprauge, Kozlowski, Hunten. Distribution and Abundance of Sodium in Mercury’s Atmosphere, 1985 -1988. 1997. Icarus 129, page 512 25

R EFERENCES AND I MAGES C ONT .  Image slide 8: Sprauge, Kozlowski, Hunten. Distribution and Abundance of Sodium in Mercury’s Atmosphere, 1985 -1988. 1997. Icarus 129, page 514  Image slide 9: Sprauge, Kozlowski, Hunten. Distribution and Abundance of Sodium in Mercury’s Atmosphere, 1985 -1988. 1997. Icarus 129, page 508  Image slide 14: Cassidy, Timothy. PowerPoint presentation 26