arXiv:1403.8146v2 [physics.pop-ph] 29 Apr 2014 oeis otntbytoefo the dis- from recent process more those the from of notably that clear diversity most also apparent enormous is coveries, now It an is systems. produces life It planetary there formation is out planet common us? are of How things kill many can common how Earth? Exactly that How the universe? of unusual? the size in or the architecture typical planets the for System are Is Solar philosophers include: our of questions of minds These ques- the several nagged millennia. answering have of which possibility the tions up opened has uha vn u ol olpermral quickly. remarkably collapse survive that would to shown but unlikely event have be an (2009) only such not al. out- would et civilization SNAP Munz human various by of pro- scenarios spread modeling to break consciously itself Detailed to host which condition. the from of the platform use mobile its as a far vide so particu- in Spontaneous is nefarious condition of larly contagious that as highly This to is referred Zombie-ism. detail often which (SNAP), great phenomenon Psychosis in Necro-Animation recent studied more been A ty- has influenza, smallpox. cholera, and include phus, centuries virus. recent homo- in affected the have sapiens by which caused pandemics breakdowns lethal of Particularly genetic populations to various on due impact animals which hosts. devastating outcomes a as destructive had animals in have the result use and occasionally which species These viruses animal and bacteria between the relationships symbiotic true, by a be have may may common This is consequence. life negative issue. that serious deduction this surely positive fact resolving is a The but common for Solar relatively common. our news is are to good life planets exterior if Earth-size life determine that for thus search correla- and the a System within such lies establishing common. for tion exceptionally motivation are primary The planets terrestrial-size that h eeto fpaesotieo u oa System Solar our of outside planets of detection The h vlto flf nErhhsbe accompanied been has Earth on life of evolution The rpittpstuigL Necronomicon using the typeset in Preprint publication for Submitted a eqatfid efrhrageta ti atro planetary of matter era. a space-faring headings: future is Subject a it planet in SNAP-contaminated that worlds potential argue these catalog further and apocalypse We monitor how zombie carefully Equat demonstrate a quantified. We Drake where be Zombie atmospheres Paradox. may the the Fermi in of the present use for dang W signatures the explanation serious through possible a their Zombie-ism. Earth a presents of or to universe Zone posed (SNAP), the Habitable danger Psychosis in the life Necro-Animation of prevalent Spontaneous occupants of the conclusion or being a of planets distribution The these common. of exceedingly are planets terrestrial sw er oeaottefeunyadsz itiuino exopla of distribution size and frequency the about more learn we As 1 etrfrGoa xicinPnei oto,Subterrane Control, Pandemic Extinction Global for Center 1. 2 ER-ILGCLEPAAINFRTEFRIPARADOX FERMI THE FOR EXPLANATION NECRO-BIOLOGICAL A A lntr ees nttt obeDvso,CaeuMor Chateau Division, Zombie - Institute Defense Planetary INTRODUCTION T E tl mltajv 5/2/11 v. emulateapj style X srbooy–paeaysses–zmi apocalypse zombie – systems planetary – astrobiology umte o ulcto nteNecronomicon the in publication for Submitted tpe .Kane R. Stephen Kepler mission, ABSTRACT 1 rnkSelsis Franck & ucm facmlt xicineetoccurring. of likely event work the extinction The quantifies complete accurately albeit a 2007). more of recover, outcome (2009) (Brooks to al. extinction able et of are Munz unlikely brink humans an the which presents at in it de- result although Z” War scenario end down “World such break novel one defenses, rapidly The picts will such civilization. outbreak with existing the Even any prob- of scale survival global been 2009). the the also maximize 2003, has to (Brooks outbreak detail ei- ability an great In such in from explored 2013). defense natural (Swain case, both engineering ther from genetic result a and equally found The evolution and could investigated outbreak 2012). been SNAP Kay has condi- zombie-ism 2011; of and Vuckovic the science literature 2005; of both reality (Russell in depicted the cinema extensively Earth, been has on tion outbreaks will SNAP it of that ensures This uncontrollably. desire usually, costs. insatiable and, all quickly at an spread virus host the the spread upon to max- living is bestowing infect condition by the to of imized nature condition infectious viral The dangerous organisms. most the edly sobering 6. final Section the in provide we conclusions and terrifying is and 5 signatures such Section detecting in for discussed window observing Section The in necro- identification resulting 4. for the potential establish their to and released. used signatures gases then the is de- and process we This process 3 Section decomposition SNAP-contaminated In the SNAP, Earth. scribe of of to proximity nature numbers their and dangerous planets, possible the the outline we quantify occurred. 2 bio- have of that Section apocalypses full In indicate zombie planets where of diseases remains reservoirs decay infectious harbor may of universe the studies with bined lhuhdtcigtencosgaue fworlds of necro-signatures the detecting Although cases documented been yet not have there Although undoubt- is Psychosis Necro-Animation Spontaneous com- discoveries exoplanet recent how discuss we Here nBne 2 no qae a rnic,USA Francisco, San Square, Union 32, Bunker an 2. sVvns odax France Bordeaux, ts-Vivants, ia eid ntr eut nmany in results turn in periods bital a aeocre ota h risk the that so occurred have may H ELT FTEDANGER THE OF REALITY THE nodrt xld otc with contact exclude to order in s 2 o n hwhwti evsas serves this how show and ion rdet h iko spreading of risk the to due er otsas eew hwthat show we Here stars. host oietf h eutn necro- resulting the identify to ees n euiyta we that security and defense uniyteetn fthe of extent the quantify e es eaedsoeigthat discovering are we nets, 2 Stephen R. Kane & Franck Selsis

your pulse!1 Furthermore, the projected frequency of SNAP plan- ets explains a contradiction which has long troubled the proposition that intelligent life is common: the Fermi Paradox. This premise of the paradox is that the timescale for extraterrestrial civilizations to spread throughout the galaxy is small compared with stellar life- times and so we should have encountered our neighbors by now. Our work here shows the resolution of the para- dox to be quite simple. The desolation of a civilization requires only that they encounter a case of SNAP dur- ing their exploration phase and their entire civilization will collapse. Let us not repeat history by rushing in to where our predecessors ought to have feared to tread.

3. DECOMPOSITION

Fig. 1.— Histogram of all stars within 100 parsecs of the Earth Now that your trousers are presumably the appropri- (light gray) and the systems which are likely to contain SNAP- ate shade of brown, we must determine how the SNAP infected planets (dark gray). This shows that there are likely more planets may be detected remotely and thus avoid them than 2,500 SNAP-contaminated systems in close proximity to the like ... well, the plague. To quantify this, we first need to Solar System. identify what it is we are actually looking for. A defining outcome of a zombie apocalypse is the death of all ani- where a zombie apocalypse has occurred, we can also mal life on the planetary surface. This will result in the estimate the number of worlds which are affected in this transfer of a substantial fraction of the total biomass to way. To accomplish this, we use a modified version of the the atmosphere through the process of decomposition. well-known Drake Equation, the original of which takes All animals undergo similar stages of decomposition: the following form: Fresh, Bloat, Active Decay, Advanced Decay, and Dry re- mains. The primary decomposition stages during which × × × × × × N = R⋆ fp ne fl fi fc L (1) the purging of gases and fluids occur are the Bloat and Active Decay stages. For Earth-based animals, the pri- where the purpose is to calculate N which is the num- mary gases produced during this process are carbon diox- ber of advanced civilizations in the galaxy with radio- ide, hydrogen sulfide, ammonia, and methane. The ex- communication capability. The other variables include tent to which this translates into strong signatures within R (average rate of star formation), f (fraction of stars ⋆ p the planetary atmosphere depends on the relative mass with planets), n (average number of life-capable planets e of the biosphere being converted to these gases. Hu- per star), f (fraction of planets with life), f (fraction of l i mans constitute roughly 350 million tonnes of terrestrial planets with intelligent life), f (fraction of civilizations c biomass with an additional 700 million tonnes available that develop radio technology), and L (length of time via domesticated animals. The cross contamination of such civilizations communicate). For a zombie outbreak SNAP for humans versus animals varies depending on to occur, there is no reason to a priori assume that intel- the movie/literature source. Even if humans are the only ligent life is required. Thus the modified Zombie Drake species to succumb to such an infection, we can expect Equation is as follows: the levels of decomposition gases described above to at Nz = R⋆ × fp × ne × fl × fz (2) least double and probably increase by factors of several. Incidentally, the animal species on Earth with the high- where Nz is the total number of SNAP-contaminated est biomass is antarctic krill who apparently have natu- planets and fz is the fraction of planets where an out- ral selection all figured out. However, it’s unknown what break has utterly destroyed the local population. a zombie apocalypse involving krill would look like and There is strong evidence to suggest that the appear- there is certainly a cinema niche awaiting any film direc- ance of Earth-based life occurred at a very early stage tor who would care to portray it. of Earth’s history, probably at least as early as 3.9 bil- lion years ago. This lends credence to the hypothesis 4. DETECTING NECRO-SIGNATURES that life is indeed a natural consequence of having suit- The gases released by the decomposition process de- able conditions, which is a terrestrial planet within the scribed above may be used to remotely detect the zom- Habitable Zone of the star. Based on reasonable esti- bie afflicted worlds. In particular, the strong atmospheric mates of the frequency of terrestrial planets with such presence of CO2, H2S, CH4, and NH3 will reveal those lo- conditions, we use Equation 2 with a conservative fz cations where massive amounts of death and decay have value of 10%. Shown in Figure 1 is a histogram of all recently taken place. The strength of the respective sig- stars within 100 parsecs of Earth based on data from the natures for these gases in emission and transmission spec- Hipparcos mission. The dark region shows an estimate tra will vary greatly. The presence of increased levels of of the distribution of nearby stars which could have a H2S for example will have a relatively weak associated SNAP-contaminated planet based on the above assump- tions. This would mean that there are more than 2,500 1 If there’s no pulse, you could be our SNAP patient zero. The such systems within 100 parsecs of Earth. If that doesn’t fact that you’re reading this makes it unlikely. However, just to be scare the bejeezus out of you then you may need to check sure, test if you can speak an intelligible sentence.

A Necro-Biological Explanation for the Fermi Paradox 3

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Fig. 2.— Thermal emission spectrum and transmission spectrum of an Earth-analog affected by SNAP. Left: Thermal emission as received at 10 pc. Right: Variation in the apparent radius given by the transit depth as a function of wavelength. The blue curves are for the present Earth. The green and red curves are for a moderate and major infection of the biosphere. See text for the corresponding atmospheric properties. Spectra computed assuming cloud-free conditions, with the code PAS (Post-Apocalyptic Spectroscopy, courtesy of Marcelino Agundez, Madrid). signature. However, there are other atmospheric pro- cesses that occur as part of apocalypse-level decomposi- tion that more than compensates and delivers an unam- biguous necro-signature. Figure 2 shows the spectral signatures associated with a zombie apocalypse on an Earth-like planet. The left panel shows the transmission spectrum that can be ob- tained by transit spectroscopy while the right panel shows the thermal emission of the planet that can be observed either by secondary eclipse spectroscopy or in- frared nulling interferometry if the planet does not tran- sit its host star. Two cases are compared to present Earth. One is a moderate SNAP with less than 10% of an Earth-sized human and animal biomass affected by the infection. This results in enhanced levels of some at- mospheric gases: 2 PAL (Present Atmospheric Level) of Fig. 3.— CO2, and 5 PAL of CH4, N2O and NH3, due to the pu- The concentration of decomposition gases as a function trefaction and disruption of the nitrogen cycle (known as of time for both “basic outbreak” and “latent infection” scenarios. For an Earth-size biomass, necro-signatures will remain at their the Savini effect). This also results in an increased green- peak amplitude for at least a year. house warming and a mean surface temperature of 296 K instead of 288 K on present Earth. We also modeled a dow in which signatures of the apocalypse may persist in major SNAP event, assuming a biomass twice the one on the atmosphere. present Earth and a 90% infection. In this case, we find There are various models which may be used to deter- 4 PAL of CO2, 20 PAL of CH4,and 50 PAL N2O and mine the spread of infection and thus the rise of decom- NH3. Spectral features associated with all these species position gases in the atmosphere. A broadly applicable reveal the rise of zombies at a planetary scale. model to use for the infection rate is the basic model If you detect a signature such as the one described outbreak scenario of Munz et al. (2009) since we are not above, here is what you should do. First, hyper-ventilate assuming that the primary species with the infection is into a paper bag. Second, call the person who occupies intelligent (yes, including Earth). This model predicts an your country’s highest office whilst screaming hysteri- unimpeded spread of the infection and a correspondingly cally. Neither action will help the situation but it will rapid rise in decomposition gases. This is shown by the make you feel like you’ve actually done something use- solid line in Figure 3. Alternatively, one may consider ful. the latent infection model in which a certain fraction of 5. the zombies are destroyed as they are created by the as- OBSERVING WINDOW tute uninfected population. As shown by the dashed line Due to the animation aspect of a zombie and its de- in Figure 3, this slows the release of decomposition gases sire to infect others, the corpse is invariably exposed to into the atmosphere but results in only a small delay. the elements. Additionally, conflict between the zombies In either case, the 100% fatality rate produces a period and those not yet infected will produce high temperature of at least one year during which the necro-signatures conditions. The combination of these two environmen- described in Section 4 will be at their maximum ampli- tal effects will be to accelerate the rate of decomposition tude, gradually decreasing over the following couple of (see Section 3) and thus produce a relatively brief win- years. For biomasses larger than that currently present 4 Stephen R. Kane & Franck Selsis on Earth, this period of maximum amplitude will be pro- scary as being eaten by a zombie and so we justifiably portionally longer. Removal of these gases from the at- ignore those other possibilities. mosphere assumes absorption by liquid water oceans and The best chance that we as a civilization has of pre- other mineral chemical reactions. However, it is possible venting a future encounter with a zombie virus is to that a new equilibrium is reached by which the necro- carefully monitor and catalog the SNAP-contaminated signatures could persist for much longer. planets. Although this requires the dedicated use of the James Webb Space Telescope (JWST) to perform this 6. CONCLUSIONS task, this will likely be insufficient to meet the challenge We have shown that there is a significantly non-zero of monitoring all stars with the needed signal-to-noise. probability that in the search for life in the universe we Thus we strongly advocate the construction of a fleet of will also encounter large amounts of undeath. Any per- no fewer than 10 JWSTs with increased apertures (12 son who has been exposed to even a relatively benign meters should do the trick!). These should be designed zombie film understands the threat posed by this heinous to also operate together as a nuller interferometer so they malady. This is not to be trifled with. Therefore the risk can survey non-transiting nearby exoplanets, which rep- imposed of encountering a SNAP-contaminated planet resent the main threat. Transiting planets are generally cannot be overstated. far away, and we can all agree that an undead neighbor is We have shown that the sign-posts for SNAP worlds immensely more scary than a distant zombie. Whatever are present and detectable in exoplanet atmospheres. We the course of action, we must actively strive to address have also shown that these signatures may not persist for the threat and to mitigate the risk of annihilation by an very long in the upper atmosphere which emphasizes the exoplanet zombie infection. need for continuous observations. An extension of the necro-signature would be produced by worlds where ad- ACKNOWLEDGEMENTS vanced civilizations existed due to the considerable time The authors would like to thank Vetter Brewery in required for the breakdown of the industry infrastructure Heidelberg for the hefeweizen-fueled stagger which in- left behind. One may well point out that there are nu- spired this work. Stephen would also like to thank Sean merous scenarios other than a zombie apocalypse that Raymond for not turning into a zombie and eating his could equally quell all life on a planet. However, we ar- office-mate Franck without whom this work would not gue that none of those scenarios are anywhere near as have been possible.

REFERENCES Brooks, M. 2003, “The Zombie Survival Guide: Complete Russell, J. 2005, “Book of the Dead: The Complete History of Protection from the Living Dead” Zombie Cinema” Brooks, M. 2007, “World War Z: An Oral History of the Zombie Swain, F. 2013, “How to Make a Zombie: The Real Life (and War” Death) Science of Reanimation and Mind Control” Brooks, M., 2009, “The Zombie Survival Guide: Recorded Vuckovic, J. 2011, “Zombies!: An Illustrated History of the Attacks” Undead” Kay, G. 2012, “Zombie Movies: The Ultimate Guide”, 2nd edition Munz, P., Hudea, I., Imad, J., Smith, R.J. 2009, Infectious Disease Modelling Research Progress, pp. 133-150