slideshow 1 slideshow 2 slideshow 3 slideshow 4 slideshow 5 slideshow 6

You are here

Lucille Le Corre Personal/Professional Page

NASA funded grants

NNH15ZDA001N-HAYB2: Hayabusa2 Participating Scientist

Constraining Surface Properties of Asteroid 1999 JU3 using Hayabusa2 Optical Navigation Camera Clear and Color Images. PI: Lucille Le Corre (PSI), Co-Is: Jian-Yang Li (PSI), Kris Becker (USGS), Coll.: Robert Gaskell (PSI).

Investigating hydrated silicates and organic compounds on asteroid 1999 JU3. PI: Driss Takir (USGS), Co-Is: Lucille Le Corre (PSI), Charles Hibbitts (APL), Joshua Emery (UTK).

NNH14ZDA001N-SIMPLEX: Small, Innovative Missions for Planetary Exploration

DAVID: Diminutive Asteroid Visitor using Ion Drive. PI: Geoffrey Landis (NASA), Science PI: Ralph Harvey (CWRU), Coll.: Vishnu Reddy (UA), Lucille Le Corre (PSI).

NNH13ZDA001N-PMDAP: Planetary Mission Data Analysis Program

Restoring Dawn Framing Camera Multi-Band Data of Vesta to Full Spatial and Photometric Accuracy. PI: Lucille Le Corre (PSI), Co-Is: Kris Becker (USGS), Robert Gaskell (PSI), Jian-Yang Li (PSI), Vishnu Reddy (UA), David Blewett (APL), Paul Lucey (UH).

NNH12ZDA001N-PMDAP: Planetary Mission Data Analysis Program

Mineralogical Mapping of Asteroid Itokawa using Hayabusa AMICA Camera Multi-Spectral and NIRS Spectrometer Data. PI: Vishnu Reddy (UA), Co-Is: Lucille Le Corre (PSI), Kris Becker (USGS), Jian-Yang Li (PSI), Coll.: Robert Gaskell (PSI).

Publications list

Bright spots on (1) Ceres

Bright spots seen by NASA’s Dawn spacecraft on the surface of dwarf planet Ceres are likely salt deposits. Ceres has more than 130 bright areas, and most of them are associated with impact craters. Observations from Dawn’s Framing Camera suggest the occurrence of salts originating from Ceres’ interior. These salts are consistent with a type called magnesium sulfate. We reviewed three possible analogs for the bright spots (ice, clays and salts). Salts are the best possible explanation of what we see on the surface of Ceres. These salt-rich areas were left behind when water-ice sublimated in the past. Impacts from asteroids would have unearthed the mixture of ice and salt. The location of some bright spots also coincide with places where water vapor was detected by other spacecraft.

Sublimation in bright spots on (1) Ceres

Calibration equations for the compositional analysis of asteroid Itokawa using Hayabusa NIRS data

The Hayabusa spacecraft was launched in May 2003 to rendezvous with Apollo-type NEA (25143) Itokawa and bring back a sample to the Earth. The spacecraft arrived at the asteroid in September 2005 and spent three months collecting science data in a station-keeping heliocentric orbit. Ground-based observations and analysis of samples returned by the Hayabusa spacecraft have confirmed the LL chondrite composition of Itokawa. While laboratory calibrations to extract olivine and pyroxene compositions from near-IR reflectance spectra (0.7-2.5 µm) of S-type asteroids currently exist, detailed analysis of the NIRS (Near InfraRed Spectrometer) data could not be accomplished till now due to its limited wavelength range (0.85-2.1 μm). The NIRS data has only been analyzed using simple ‘curve matching’ technique to link the surface composition of Itokawa to LL chondrites. Therefore, we published calibration equations used for extracting the mineralogy of Itokawa from the Hayabusa NIRS dataset. These equations can be used to extract olivine and pyroxene compositions from the NIRS data and map their distribution across the surface of the asteroid.

Spectral calibration for deriving surface mineralogy of Asteroid (25143) Itokawa from Hayabusa Near-Infrared Spectrometer (NIRS) data

False color composite image of Itokawa created with AMICA color images.

Exploring exogenic sources for the olivine on Asteroid (4) Vesta

Olivine is expected on the surface after the excavation of the crust and the mantle due to the giant impact forming the Rheasilvia basin at the south pole of Vesta. I published a study in 2015 presenting an alternative interpretation for the few olivine-rich sites observed by the Dawn spectrometer. I proposed that the olivine material has been brought by exogenic impactors such has ordinary chondrites, which contain olivine as well. I presented arguments using evidence from the HED meteorites (Howardites-Eucrites-Diogenites) and comparison with laboratory spectra of meteorites.

Exploring exogenic sources for the olivine on Asteroid (4) Vesta

Exogenic olivine on Vesta from Dawn Framing Camera color data

Impact melt on Vesta?

NASA’s Dawn spacecraft entered orbit around asteroid Vesta in July 2011 for a year-long mapping orbit, which allowed for complete imaging of the surface with the Dawn Framing Camera (FC) clear and color filters. Vesta is one of the most colorful asteroids observed by any spacecraft so far. Just after receiving and processing the color images acquired during the approach phase (~500meters/pixel and 5200 km away from Vesta), we noticed some enigmatic “orange” material. This vestan terrain was discovered using ratios of color images and combining them in a color composite. This particular color scheme is called Clementine color ratio map because it is using almost the same filters than for the color images of the Moon acquired by the Clementine mission.

This “orange” material exhibits a specific behavior as observed through the FC color filters: a red spectral slope, and therefore is seen in FC ratio images (with red=0.75/0.45 microns, green=0.75/0.92 microns, and blue=0.45/0.75 microns) as orange or red. In the Clementine color composite, the green channel helps quantify the pyroxene absorption band depth at 0.90 microns (greener areas have higher ratio, i.e. deeper band). The two other channels will vary depending on the visible spectral slope (redder areas have positive visible slope; bluer areas have negative visible slope).

We then looked at images with higher spatial resolutions from the High-Altitude Mapping Orbit (HAMO) phase and Low-Altitude Mapping Orbit (LAMO) phase to figure out the geology of this intriguing surface unit. We noticed different types of “orange” deposits on the surface of Vesta. FC images revealed some fresh-looking craters like Cornelia or Rubria showing impact ejecta rays made of “orange” material (figure 1), several diffuse “orange” ejecta around medium size impact craters 34-km diameter Oppia and 30-km diameter Octavia (figure 2), as well as numerous “orange” deposits (one example in figure 3) with a round shape (lobate) distributed all around Rheasilvia’s basin rim (map in figure 4). Even though some of these “orange” deposits are not directly linked with nearby impact craters, our observations suggest an impact related origin. We mapped the distribution of all of the lobate “orange” material and the “orange” ejecta and we found that there are all located outside the Rheasilvia basin, which suggests a link with the basin’s formation. Several possible options for the nature of the “orange” material were investigated using the three instruments onboard the Dawn spacecraft. For example we looked at the possibility of excavation of a deep lithology (rock layer) during impacts, the presence of metal delivered by impactors coming from outside of Vesta, and impact melt (regolith material melted due to impact events). By studying the geomorphology and composition of this material and exploring possible meteoritical analogs, we concluded that the most probable origin for the “orange” material on Vesta is impact melt. The vestan regolith sometimes melted due to the heat generated by impacts and then redistributed inside and around the crater forming parts of the ejecta blanket.

For further information on the “orange” material, please check the article corresponding to this study here or here free of charge.

Figure 1. Clementine ratio images in perspective views of Cornelia (A) and Rubria (B) craters showing “orange” ejecta rays.

Clementine ratio images in perspective views of Cornelia and Rubria craters showing “orange” ejecta rays.

Figure 2. Clementine ratio images in perspective views of Oppia and Octavia craters showing “orange” diffuse ejecta material and their corresponding color-coded topography on the right side.

Figure 3. FC color ratio image (60 m/pixel) overlaid on a mosaic of clear filter images (16 m/pixel) of patche of “orange” material with rounded edges.

Figure 4. Mapping of the “orange” material in black overlaid on a color-coded topographic map. Rheasilvia impact basin’s rim is indicated in black line, Veneneia in red.

Delivery of dark material to Vesta via carbonaceous chondritic impacts

I am co-author of an investigation published in Icarus in 2012 on the nature of the dark material on Vesta. We concluded that most of the very low albedo material on Vesta is formed by contamination from exogenous carbonaceous chondrites. These new results strengthen the existing link between Vesta and the HEDs, which contain carbonaceous inclusions. I presented the possibility of detecting such material on Vesta in a previous paper published in Icarus in 2011, and discussed how to do it using FC filters.

Dark material in Cornelia crater.

Cornelia crater

Delivery of dark material to Vesta via carbonaceous chondritic impacts

How to characterize terrains on 4 Vesta using Dawn Framing Camera color bands?

Detection of serpentine in exogenic carbonaceous chondrite material on Vesta from Dawn FC data

Distinctive space weathering on Vesta from regolith mixing processes

Pitted Terrain on Vesta and Implications for the Presence of Volatiles

Other Dawn related papers:

Optical space weathering on Vesta: Radiative-transfer models and Dawn observations

Comparing Dawn, Hubble Space Telescope, and ground-based interpretations of (4) Vesta

Global photometric properties of Asteroid (4) Vesta observed with Dawn Framing Camera

Color and Albedo Heterogeneity of Vesta from Dawn

Page maintained by
lecorre [at] (L. Le Corre)

PSI, a Nonprofit Corporation 501(c)(3), and an Equal Opportunity/M/F/Vet/Disabled/Affirmative Action Employer.
Corporate Headquarters: 1700 East Fort Lowell, Suite 106 * Tucson, AZ 85719-2395 * 520-622-6300 * FAX: 520-622-8060
Copyright © 2019 . All Rights Reserved.