dawn: exploring dichotomies across space and time dawn mission speaker’s kit dawn epo teams

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Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

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Page 1: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Dawn: Exploring Dichotomies across Space and Time

DAWN Mission Speaker’s KitDawn EPO Teams

Page 2: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

So why did Dawn’s scientists choose to look at the asteroid belt? To explore the earliest stage of our solar system To understand how planets like ours formed!

Dawn will use ion propulsion to explore two complementary protoplanets, Vesta and Ceres, by:

Mapping their surfaces to understand their geology & composition Determining how and when the bodies formed And understanding the internal and external forces that shaped them

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Page 3: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Why Ceres and Vesta?

• Vesta and Ceres are protoplanets, the largest of the asteroids and survivors of the early solar system– They were amongst the first bodies to form– They are differentiated like bigger planets, but smaller than our moon

• Vesta was volcanically active like our moon, while Ceres is made of ice and rock like Jupiter’s moons– Studying Ceres & Vesta together tells us about how a planet’s size and distance

from the sun affect its formation

Page 4: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

What is an asteroid, really?

• There isn’t a good definition

• Generally, a small, rocky body orbiting ~inside the orbit of Jupiter

• Most are found in the main belt between Mars & Jupiter (which doesn’t look anything like this) -->

Image credits: Lucasfilm

Page 5: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

What are Asteroids made of?

• Bright, dry, rocky asteroids like Vesta dominate the inner asteroid belt

• Dark, hydrated, and icy asteroids like Ceres dominate the outer belt

• Ceres and Vesta are big enough to differentiate (like the Earth), and thus are also called “protoplanets”

Page 6: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Asteroids come in all shapes & sizes…but protoplanets are round!

950 km

Ceres

Vesta

Pallas

Ida

Gaspra

Annefrank

Itokawa

Eros

Image credits: NASA & STScI (HST)

Page 7: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Fiery Vesta: Differentiation and the HED meteorites

Page 8: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Vesta• Discovered by Heinrich Olbers in

March 1807• Largest basaltic asteroid

• 265 km mean radius• Third largest asteroid!• Second most massive at 2.7×1020

kg• Density of 3750 kg/m3

• Differentiated• Basaltic (like Hawaii’s volcanoes)• Distinct surface regions• Implies early formation while 26Al

was an energy source

• Likely parent body of the HED meteorites!

Image credit: STScI (HST)

Page 9: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Vesta

Model rotated to show the south pole!

Page 10: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Fiery Vesta’s BasalticVisible & Infrared Spectrum

Page 11: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

HED Meteorites• Howardites:

– Clasts of Eucrite and Diogenite material

• Eucrites: – plagioclase & pyroxene– Crust?

• Diogenites:– Orthopyroxene & olivine– Mantle?

Figure credits: Pieters et al. (2006)Dar al Gai 844, image courtesy R. Pellison-- http://www.saharamet.com

Page 12: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Vesta’s South Pole

Figure credits: Pieters et al. (2006), after Takeda et al. 1997, Thomas et al. 1997

Page 13: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Icy Ceres: Dwarf Planet

Page 14: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Ceres• Discovered in 1801 by

Piazzi• Orbital elements:

– a=2.767 AU, – e=0.097, – i=9.73, – P=9.076 hrs

• Largest body in asteroid belt – Mass: 9.46±0.04×1020 kg– 1/3 mass of asteroid belt!– Density: 2100 kg/m3

– Albedo 0.1

Image credit: STScI

Page 15: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Icy Ceres?• Size and shape-

• Oblate spheroid—just like the Earth

• Mean radius of 950 km

• Other unique attributes:• Spectra of its surface look

similar to clays• It has no obvious

topography• It has no impact family

and…• NO METEORITE ANALOG!

• WHY?

…it’s probably made of ICE!

• Ceres’ density, 2100 kg/m3, and shape tells us its interior is a mixture of ice and rock.

Image credit: STScI

Page 16: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Ceres’ SurfaceAt one point, Ceres was thought

to have frost on its surface, and though this now looks unlikely, there is still a strong case for water.

• What is there:– Clays? – Brucite (Br), – Magnesium (Mg)?– Hydration (OH)?

• Possibilities:– 3.3 μm- aromatic hydrocarbon

or ammonium-bearing clays– 3.8 μm- carbonates

• How do these minerals form?– Water-rock reactions!

Figure credit: Rivkin et al 2011

Page 17: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Ceres’ Probable Interior

Figure Credit: McCord & Sotin, 2005

Page 18: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

The DAWN Spacecraft

Page 19: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams
Page 20: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

• Two redundant framing cameras (1024 x 1024 pixels, and 7 color filters plus clear) provided by Germany (MPS and DLR)

• VIR, a visible and infrared mapping spectrometer (UV to 5 microns) provided by Italy (INAF and ASI)

• GRaND, a Gamma Ray and Neutron Detector built by LANL and operated by PSI

• A Radio Science Package provides gravity information

• Topographic models will be derived from off-nadir imaging

Dawn’s PayloadFraming Camera

VIR

GRaND

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Page 21: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Spacecraft

Page 22: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Dawn’s Interplanetary Trajectory

Thrust

Coast

Launch Sep ‘07

Mars gravity assistFeb ‘09

Vesta arrivalJuly ‘11

Vesta departureJuly ‘12

Ceres arrivalFeb ‘15

End of missionJul ‘15

Earth today

Dawn today

Vesta today

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Page 23: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

At each target, Dawn will:Acquire color imagesCompile a topographic mapMap the elemental compositionMap the mineralogical compositionMeasure the gravity fieldSearch for moons

Dawn Mission Itinerary

LaunchSep 2007

Mars Gravity AssistFeb 2009

VestaJuly 2011 – July 2012

CeresFeb 2015 – July 2015

Page 24: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Dawn will explore Vesta using its specialized instrumentation.

– Composition will be mapped by VIR (1.0 to 5.0 m) and FC color filters

– Topography, impact history and geology will be mapped by the Framing Camera

– Elemental abundances will be determined by GRaND

– Crustal thickness and interior structure will be determined by gravity from radio science

Next up:Dawn at Vesta(Jul ‘11- Jul ‘12)

Page 25: Dawn: Exploring Dichotomies across Space and Time DAWN Mission Speaker’s Kit Dawn EPO Teams

Any Questions??

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Dawn’s Launch, Sept. 27 2007