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Planetary Vision 2050 Workshop 2017 (LPI Contrib. No. 1989) 8031.pdf

The Timeline. A. J. Berliner1 and C. P. McKay2, 1University of California Berkeley, Berkeley, CA 94704, [email protected], 2Space Division, NASA Ames Research Center, Mountain View, CA 94075.

Introduction: Terraforming, the transformation of particularly the winter South Polar Cap, and any CO2 a so as to resemble the so that it can sup- that is absorbed into the cold ground in the polar re- port widespread , has been described as a grand gions. Once the warming starts all this releasable CO2 challenge of both space sciences and synthetic will go into the . Thus, it is important to [1,2]. We propose the following abstract on a know the total before warming starts. Current esti- Terraforming timeline as a guide to shaping planetary mates of the releasable CO2 on today range from science research over the coming century. a little more than the present thin atmosphere to values Terraforming Mars can be divided into two phases. sufficient to create a pressure on Mars equal to the sea The first phase is warming the planet from the present level pressure on Earth. is a fundamental re- average surface of -60ºC to a value close quirement for life and necessary constituent of a to Earth’s average temperature to +15ºC, and re- breathable atmosphere. The recent discovery by the creating a thick CO2 atmosphere [3,4,5,6] This warm- Curiosity Rover of nitrate in the soil on Mars (~0.03% ing phase is relatively easy and quick, and could take by mass) is therefore encouraging for terraforming [7]. ~100 years. The second phase is producing levels of O2 The current measurements only pertain to surface sam- in the atmosphere that would allow humans and other ples at the Curiosity site but include windblown sand large mammals to breath normally. This oxygenation and ancient sedimentary mudstones. For terraforming phase is relatively difficult and would take 100,000 we need to know the total amount on the planet and years or more, unless one postulates a technological given the high solubility of nitrate it may well be con- breakthrough [6]. centrated in specific locations. Pre-Terraforming: Before any terraforming be- The presence and of will defi- gins, some basic questions must be addressed by robot- nitely affect plans for terraforming. If there is no life ic and human missions to Mars. These are: (1) The on Mars, then the situation is relatively straightfor- amount of H2O present on Mars? (2) The amount of ward. However, even after extensive exploration it CO2 present on Mars as gas, as ice, or absorbed on may be hard to conclude that life is completely absent soil? (3) The amount of nitrate in the soil on Mars? (4) on Mars rather than simply not present at the specific And, finally, the presence of life, alive or revivable, locations investigated. If life is discovered, then the and the relationship of that life to Earth life. The an- nature and relationship between the Martian life and swers will be crucial to planning any terraforming ef- Earth life must be determined. If Martian life is related fort. However, there is also a fundamental question to Earth life – possibly due to meteorite exchange --- about terraforming itself that we must answered on then the situation is familiar and issues of what other Earth before terraforming can begin: . (5) What is the types of Earth like to introduce and when must be ad- purpose and ethical approach for making Mars habita- dressed. However, if Martian life in unrelated to Earth ble? It may be impossible to arrive at a unanimous and life and clearly represents a second genesis of life then definitive answer for this, but at the least we need an significant technical and ethical issues are raised. operational consensus. The question of possible Martian life leads to the Adequate inventories of water, , and fifth question that must be addressed before terraform- nitrogen (nitrate) present on Mars are key to the practi- ing begins. But the overarching question is why, and cality of making a on that planet. We know for who whom, are we altering Mars? If we are deter- that Mars has enough H2O to supply clouds in the sky, mined to make Mars like the present Earth – as implied rain, rivers and lakes. Presently, this H2O is mostly in in the word “terraforming” – then this requires certain the form of ice in the polar regions and polar caps, but levels of O2 and places upper limits on toxic gases once Mars is warmed this will melt. Carbon dioxide is such as CO2. Alternatively, if we are interested in mak- needed to provide a thick atmosphere to contribute to ing Mars a planet rich in life, but not necessarily a the warming and which will constitute the thick at- world in which humans can move about unprotected, mosphere at the end of the warming phase. While CO2 then the presence of a thick CO2 may be an adequate may be present on Mars in vast quantities tied up in goal. carbonate minerals, this form is not easily released as Warming Phase (~100 years): The primary chal- gas in the warming phase. Only the CO2 that is easily lenge to making Mars a world suitable for life is warm- released as gas as the temperature increases will con- ing that planet and creating a thick atmosphere. A thick tribute to the atmosphere during the warming phase. warm atmosphere would allow liquid water to be pre- This includes the small amount of CO2 in the present sent and life could begin. Warming an entire atmosphere, the CO2 that is contained in the polar caps, may seem like a concept from the pages of science Vision 2050 Workshop 2017 (LPI Contrib. No. 1989) 8031.pdf

fiction but in fact we are demonstrating this capability can transform H2O and CO2 into biomass and O2 is on Earth now. By increasing the CO2 content of the much less than 100%. The only example we have of a Earth’s atmosphere and the addition of super green- process that can globally alter the CO2 and O2 of an house gases we are causing a warming on Earth that is entire plant is global biology. On Earth the efficiency of order a many degrees centigrade per century. Pre- of the global biosphere in using sunlight to produced cisely these same effects could be used to warm Mars. biomass and O2 is 0.01%. Thus the timescale for pro- Warming the Earth was not the intended purpose of ducing an O2 rich atmosphere on Mars is 10,000 17 either the CO2 release or the use of super greenhouse years, or ~ 170,000 years. In the future, synthetic biol- gases by humans and indeed we are now seeking to ogy and other may be able improve on limit both effects. On Mars we could purposefully pro- this efficiency, reducing this to about 100,000 years. duce super greenhouse gases and rely on CO2 released The 0.01% efficiency of the biosphere represents an from the polar caps and absorbed in the ground. The ecological constraint, averaging over oceans, deserts result would be a thick warm atmosphere on Mars. The and forests. The intrinsic efficiency of photosynthesis timescale for warming Mars after a focused effort of in terms of a unit leaf is much higher, about 5%. If this super greenhouse gas production is short, only 100 could be utilized over the entire area of Mars (an un- years or so. Effectively, greenhouse gases warm Mars likely possibility) then the timescale for O2 production by trapping solar energy. If all the solar incident on becomes a few hundred years [6]. Mars were to be captured with 100% efficiency, then Next Steps: Given the long-term timeline of a pos- Mars would warm to Earth-like in about sible terraforming endeavor, we propose the develop- 10 years. However, the efficiency of the greenhouse ment of a roadmap that outlines the technological pro- effect is plausibly about 10%, thus the time it would cesses and advancements required including: (1) adap- take to warm Mars would be ~100 years. This as- tation of current and future robotic Martian missions sumes, of course, adequate production of super green- for measuring specific elemental and mineral samples house gases over that entire time. The super green- such that a geolocated Martian resource database can house gases desired for use on Mars would be per be constructed; (2) mathematical modeling of Martian fluorinated compounds (PFCs) as these are not toxic, terraforming such that both Martian and Terran re- do not destroy ozone, will resist dedgradation by ultra- source costs can be calculated for a specific set of ter- violet life, and are composed of elements (C, S, and F) raform-related reactions; (3) development of computa- that are present on Mars [8]. Fluorine has been detect- tional models for biological under specific ed on Mars by Curiosity [9]. The Warming Phase on conditions in line with the Mathematical terraforming Mars results in a planet with a thick CO2 atmosphere. conditions; (4) a focused initative for The thickness is determined by the total releasable CO2 engineering organisms for Martian in-situ resource present on Mars. The temperatures are well above utilization; (5) Earth-based experimental systems for freezing and liquid water is common. An Earth-like emulating Martian conditions for local testing of bio- hydrological cycle is maintained. Photosynthetic or- logical and chemical processes; (6) development of ganisms can be introduced as conditions warm and localized para-terraforming systems for evaluating organic biomass is thus produced. A rich flora and processes in a controlled area on Martian surface and fauna are present. A natural result of this is the biolog- subsurface via probes; and (7) a planetary protection ical consumption of the nitrate and perchlorate in the agreement describing restrictions of terraforming pro- Martian soil producing N2 and O2 gas. While the pres- cesses such that Mars can be maintained for future sure is high enough that humans do not need a space studies and terraforming can be explored beyond ex- suit, they need a gas mask to provide O2 and prevent perimental and computational means. We realize that high levels of CO2 in the lungs. such a roadmap will require the input from many Oxygenation Phase (~100,000 years): To alter the communitites within space scienes, , geo- thick CO2 atmosphere of Mars produced in the Warm- sciences, and biological sciences. Thus, we argue that, ing Phase to allow for humans to breathe naturally in light of the lengthy timeline outlined above, that we requires that the O2 levels be above 13% and the CO2 “might as well start now”[10]. levels be below 1% of sea level pressure. The high O2 References: [1] A. A. Menezes et al. (2015) J. R. Soc. Inter- and low CO levels on Earth are due to photosynthesis face, vol. 12, no. 113, 2015. [2] C. P. McKay. (2011) Engineer- 2 ing Earth: The Impacts of Megaengineering Projects, 2227– which uses light to power the following transformation 2232. [3] C. P. McKay et al. (1991) Nature, vol. 352. 489–496. [H2O + CO2 = CH2O + O2 ] Where CH2O is a chemical [4] M. J. Fogg (1992) Br. Interplanet. Soc. 45, 315–329. [5] J. representation of biomass. If all the sunlight incident M. Graham. (2004) Astrobiology, vol. 4, no. 2, 168–195. [6] C. P. McKay. (2009) Explor. Orig. 1–15. [7] J. C. Stern, et al. on Mars was harnessed with 100% efficiency to per- (2015) Proc. Natl. Acad. Sci. 112, 4245–4250. [8] M. M. Mari- form this chemical transformation it would take only et al. (2005) J. Geophys. Res. E , vol. 110, no. 3, 1– 17 years to produce high levels of O2. 15. [9] O. Forni et al.( 2015) Geophys. Res. Lett. 42, 1020–1028. However, the likely efficiency of any process that [10] K.S. Robinson. (1993) “Red Mars”.