The handle http://hdl.handle.net/1887/66260 holds various files of this Leiden University
dissertation.
Author: Eistrup, C.
Title: From midplane to planets : the chemical fingerprint of a disk
Issue Date: 2018-10-16
From Midplane to Planets
The Chemical Fingerprint of a Disk
Christian Eistrup
From Midplane to Planets
The Chemical Fingerprint of a Disk
Proefschrift
ter verkrijging van
de graad van Doctor aan de Universiteit Leiden, op gezag van Rector Magnificus prof. mr. C.J.J.M. Stolker,
volgens besluit van het College voor Promoties te verdedigen op dinsdag 16 oktober 2018 klokke 10.00 uur
door
Christian Eistrup
geboren te Hørsholm, Denemarken in 1988
Prof. dr. C. Mordasini (Universit¨at Bern) Prof. dr. I.A.G. Snellen
Prof. dr. H.J.A. R¨ottgering
Christian Eistrup, 2018c
Cover artwork: adapted from “ALBEDO” by Kasper Eistrup Cover layout: Iris Nijman
Image in “Acknowledgement”-section:
http://www.clker.com/clipart-pink-elephant-12.html ISBN: 978-94-028-1202-2
An electronic version of this thesis can be found at www.strw.leidenuniv.nl/∼eistrup
Til mor, far og Astrid, for støtten til at tage springet!
The stars are for everyone to see, yet for no one to touch and control. So let go, sit back, relax, be fascinated, become curious, and wonder. The Universe can open and broaden your mind!
Contents i
Contents
1 Introduction 1
1.1 Planets and exoplanets . . . 2
1.2 Making planets . . . 3
1.3 Protoplanetary disks, and the era of ALMA . . . 5
1.4 Astrochemistry: laboratory, simulations and observations . . . 8
1.5 Combining astrochemistry and planet formation . . . 10
1.6 Comets as fossils of planet-forming material . . . 12
1.7 This thesis . . . 14
1.8 Main conclusions . . . 16
1.9 Future outlook . . . 17
2 Setting the volatile composition of (exo)planet-building material Does chemical evolution in disk midplanes matter? 19 2.1 Introduction . . . 21
2.2 Methods . . . 25
2.2.1 Physical disk model . . . 25
2.2.2 Chemical model . . . 28
2.3 Results . . . 30
2.3.1 Reduced chemical network . . . 31
2.3.2 Full chemical network . . . 34
2.3.3 Main nitrogen reservoirs . . . 36
2.4 Discussion . . . 37
2.4.1 Compositional diversity at different radii: inheritance vs reset 37 2.4.2 C/O ratio . . . 40
2.4.3 Implications for planet formation and comets . . . 42
2.4.4 Caveats of model assumptions . . . 43
2.5 Conclusions . . . 45
2.A Timescales . . . 47
3 Molecular abundances and C/O ratios in chemically evolving planet- forming disk midplanes 49 3.1 Introduction . . . 51
3.2 Methods . . . 53
3.2.1 Evolving disk model . . . 54
3.3 Results . . . 58
3.3.1 Static versus evolving disk: shifting icelines . . . 60
3.3.2 Timescales of chemical changes . . . 61
3.3.3 Varying disk masses . . . 66
3.3.4 Importance of initial abundances: inheritance vs reset . . . 67
3.3.5 O2 as a significant disk midplane molecule . . . 67
3.3.6 Caveats of model assumptions . . . 68
3.4 Discussion . . . 70
3.4.1 Iceline shifts: comparison to other studies . . . 70
3.4.2 What happens to gaseous CO? . . . 70
3.4.3 Evolving elemental ratios . . . 72
3.4.4 Impact for planet formation and planet atmospheric compo- sition . . . 75
3.5 Summary . . . 76
3.A Physical structure for 0.55 MMSN disk . . . 78
4 Formation of cometary O2 ice and related ice species on grain surfaces in the midplane of the pre-Solar nebula 79 4.1 Introduction . . . 81
4.2 Methods . . . 82
4.2.1 Ionisation levels . . . 83
4.2.2 Chemical network . . . 84
4.3 Results . . . 85
4.3.1 PSN abundance evolution . . . 85
4.3.2 Including ozone ice chemistry . . . 89
4.3.3 Exploring the sensitivity of the abundances to assumed grain- surface parameters . . . 90
4.3.4 Including a primordial source of O2 ice . . . 95
4.4 Discussion . . . 96
4.4.1 Chemical starting conditions . . . 96
4.4.2 Dependence on ionisation levels . . . 96
4.4.3 Changing Ebinfor atomic oxygen, and inclusion of O3 . . . 97
4.4.4 Narrowing down on O2ice production . . . 97
4.4.5 Activation energy for O3ice production pathway . . . 98
4.4.6 Location of O2ice production sweet spot in PSN disk midplane 99 4.4.7 Primordial origin of O2ice . . . 99
4.5 Conclusion . . . 99
4.A Appendix: additional figures . . . 100
5 Matching protoplanetary disk midplane chemical evolution to cometary compositions A chemical evolution taxonomy for comets 113 5.1 Introduction . . . 115
5.2 Methods . . . 116
Contents iii
5.2.1 Model description . . . 116
5.2.2 Statistical comparison between observations and models . . 118
5.3 Results . . . 119
5.3.1 Full sample of species . . . 119
5.3.2 Correlation for C- and O-carrying species only . . . 121
5.4 Discussion . . . 121
5.5 Conclusion . . . 127
5.A Evolving modelled abundances and cometary abundances . . . 128
Bibliography 135
English Summary 143
Nederlandse Samenvatting 149
Dansk Resum´e 155
Publications 161
Curriculum Vitae 163
Acknowledgements 167
