detection of water ice and organic molecules on asteroids
Post on 24-Jan-2016
23 Views
Preview:
DESCRIPTION
TRANSCRIPT
Detection of Water ice and Organic Molecules on Asteroids
Humberto Campins- University of Central Florida- Instituto Astrofísica de Canarias, Spain- Observatoire de la Côte d’Azur, France
UCF College of Science Dec. 3, 2010
Ice and Organics on Asteroids: 24 Themis & 65 Cybele
Accepted Sept. 9, 2010
I. Asteroids and the Early Solar System
II. Detection of Water-Ice and Organic Molecules on 24 Themis & 65 Cybele
III. Implications on Origin of Earth’s Water & Life
IV. Conclusions
Outline
V. Conclusions Water-ice and organic molecules detected on two
asteroids so far: 24 Themis and 65 Cybele
Water more abundant on asteroids than expected
Supports proposed asteroidal origin of Earth’s water and organic molecules
Helps understand origin and evolution of life on Earth and possibility of Earth-like planets around other stars
Helps case for NASA’s OSIRIS-Rex mission
I. Asteroids and the Early Solar System
• Planets, asteroids & comets formed from Solar Nebula 4.6 billon years ago
• Planets were transformed extensively • Asteroids & comets are “cosmic fossils” preserving
clues about early solar system
Asteroids and comets accreted at different distances from the Sun
Asteroids: more rock
Comets: more ice
Asteroid Belt
Asteroid Belt
24 Themis
65 Cybele
Largest fragment of a family (~ 2.5 By old) Orbiting near 3.2 AU Diameter ~ 198 km Dark (reflects only 7% of light) Rotation period: 8.4 h
I. Introduction: 24 Themis
Largest of group between 3.3 & 3.7 AU Orbiting near 3.4 AU Diameter ~ 273 km Dark (reflects only 7% of light) Rotation period: 4.0 h
I. Introduction: 65 Cybele
• Themis asteroid family resulted from a large collision and contains two small members that behave like comets
I. Introduction: Themis Family
Elst-Pizarro
176P/Linear
Orbits of the two Themis-family active asteroids not likely to evolve from comets
Spectra of both Themis-family MBCs resemble those of the larger family members and not those of comets
These small asteroids are true members of the Themis family; hence, this family probably contains water-ice
I. Introduction: Themis Family
Infrared Spectra over 7 hours (84% of rotation period)
II. Detection of Water-Ice and Organic Molecules on 24 Themis & 65 Cybele:Rotationally Resolved Observations of 24 Themis
Rotationally Resolved Observations: Ice widespread on 24 Themis
Ice
Infrared Spectra over 7 hours (84% of rotation period)
Something is missing !!!
Something is missing !!!
School of Astronomical Potions
ORGANICS: the missing ingredient
A 5% of “Ice Tholin” added to the mixture of water ice and anhydrous silicate works best!
A 5% of “Ice Tholin” added to the mixture of water ice and anhydrous silicate works best!
ORGANICS: the missing ingredient
Spectra of 24 Themis and 65 Cybele Very Similar
Spectra of 24 Themis and 65 Cybele Very Similar
Ice
Spectra of 24 Themis and 65 Cybele Very Similar
Organics
3.2 3.3 3.4 3.5 3.6
3.2 3.3 3.4 3.5 3.6 wavelength (m)
Exact Composition of Organics is Uncertain:3.4-micron absorption is produced by C-H bond
IV. Implications on Origin of Earth’s Water and life
No Water in Early Earth and Mars
• The solids that formed in the accretion zones of Earth and Mars had a very low water content
• It has been suggested that most of Earth’s water came from asteroids and comets
• More specifically, Morbidelli et al. (2000) suggested Earth’s water came from a single impact with an object formed in the outer asteroid belt
Water in Meteorites
Wet
Dry
• If Earth formed dry where did its water come from?
• The composition of Earth’s water is consistent with asteroidal and cometary contributions
• Main evidence from Deuterium to Hydrogen isotopic ratios (D/H)
IV. (cont.)Implications on Origin of Earth’s Water and life
D/H Ratios10-3
10-4
Earth Oceans
10-5
Solar Nebula
•HB •HY •HA
C Chondrites (H2O-rich meteorites)
Comets
• Water-rich meteorites have the appropriate D/H ratio to be a source of Earth’s Water
• The few comets properly observed have D/H ratios higher than Earth, so comets may have contributed to raise the D/H from the Solar Nebula value
• Asteroids and comets likely brought Earth much of its water….. and more
IV. (cont.)Implications on Origin of Earth’s Water and life
Surface of Early Earth was Molten Rock
IV. Implications on Origin of Earth’s Water and life
• Magma Oceans probably destroyed any primordial organics on Earth
• Meteorites and Comets have significant amounts of organic molecules: – the most primitive meteorites are rich in amino
acids, and – about half of the cometary dust is organic
• Hence, impacts with asteroids and comets, may have also contributed significantly to the organic molecule inventory of early Earth
• The discovery of water ice and organics on 24 Themis and 65 Cybele supports an asteroidal origin of at least some of Earth’s water and organic molecules
IV. Implications on Origin of Earth’s Water and life
Yes, for example:
• 24 Themis is a B-type asteroid, so is near-Earth asteroid 1999RQ36 the target of NASA’s proposed asteroid sample return mission: OSIRIS-Rex
• Our results improve the chances that NASA will choose this mission for full development ($710 million) in June 2011
• UCF is a member of the OSIRIS-Rex team
Any Relevance to Near Earth Asteroids?
V. Conclusions Water-ice and organic molecules detected on two
asteroids so far: 24 Themis and 65 Cybele
Water more abundant on asteroids than expected
Supports proposed asteroidal origin of Earth’s water and organic molecules
Helps understand origin and evolution of life on Earth and possibility of Earth-like planets around other stars
Helps case for NASA’s OSIRIS-Rex mission
top related