Detection of Water ice and Organic Molecules on Asteroids

1. 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

2. Ice and Organics on Asteroids: 24 Themis & 65 Cybele Accepted Sept. 9, 2010

3. Asteroids and the Early Solar System Detection of Water-Ice and Organic Molecules on 24 Themis & 65 Cybele Implications on Origin of Earth’s Water & Life Conclusions Outline

4. 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

5. 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

6. Asteroids and comets accreted at different distances from the Sun • Asteroids: more rock • Comets: more ice

7. Asteroid Belt

8. Asteroid Belt 24 Themis 65Cybele

9. I. Introduction: 24 Themis • 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

10. I. Introduction: 65 Cybele • 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

11. Elst-Pizarro 176P/Linear I. Introduction: Themis Family • Themis asteroid family resulted from a large collision and contains two small members that behave like comets

12. I. Introduction: Themis Family • 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

13. II. Detection of Water-Ice and Organic Molecules on 24 Themis & 65 Cybele: Rotationally Resolved Observations of 24 Themis Infrared Spectra over 7 hours (84% of rotation period)

14. Rotationally Resolved Observations: Ice widespread on 24 Themis Ice Infrared Spectra over 7 hours (84% of rotation period)

15. Something is missing !!!

16. Something is missing !!! School of Astronomical Potions

17. ORGANICS: the missing ingredient A 5% of “Ice Tholin” added to the mixture of water ice and anhydrous silicate works best!

18. ORGANICS: the missing ingredient A 5% of “Ice Tholin” added to the mixture of water ice and anhydrous silicate works best!

19. Spectra of 24 Themis and 65 Cybele Very Similar

20. Spectra of 24 Themis and 65 Cybele Very Similar Ice

21. Spectra of 24 Themis and 65 Cybele Very Similar Organics

22. 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

23. 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

24. Water in Meteorites Wet Dry

25. 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

26. D/H Ratios 10-5 10-3 •HB •HA Comets •HY Earth Oceans C Chondrites (H2O-rich meteorites) 10-4 Solar Nebula

27. 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

28. IV. Implications on Origin of Earth’s Water and life Surface of Early Earth was Molten Rock

29. 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

30. 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

31. 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?

32. 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