Let me conclude with a playful thought. The physiologist August Krogh (1874–1949) is best remembered for his eponymous principle, which states that “for such a large number of problems there will be some animal of choice, or a few such animals, on which it can be most conveniently studied.” Allow me one small modification. Instead of a “most convenient” animal, let us say there is a “most informative” one under the circumstances. Now ask yourself: might a similar principle apply to comparative planetology? Perhaps Mars is the best “animal” for the study of geochemical cycling before plate tectonics—better even than Earth itself. But for studies of the initiation of plate tectonics, maybe Venus is a better option. And if we want to study something like the influence of magma oceans on the atmosphere, maybe the best animal lies outside our solar system. Ease of access will tend to favor Earth as the most informative study animal, but it is not inconceivable that other benefits may sometimes outweigh mere convenience. Scientists do not want to emulate the man searching for his keys beneath the street lamp because that’s where the light is; and anyway, it is not perfect darkness outside the halo described by the lamp.
We have come a long way since Percival Lowell filled his notebooks with visions of Martian canals. Still, I find it gratifying that we can celebrate with him
the allurement we feel toward what is least like us. For the wider the separation from the familiar, the greater the parallax the new affords for cosmic comprehension… Some day, our own geology, meteorology, and the rest will stand indebted to the study of the planet Mars… and what that other world shall have taught us will redound to a better knowledge of our own, and of that cosmos of which the two form part. (Lowell 1906, 382–383)
Chapman, R. and Wylie, A. 2016. Evidential Reasoning in Archaeology. London: Bloomsbury.
Currie, A.M. 2015. Marsupial lions and methodological omnivory: function, success and reconstruction in paleobiology. Biology & Philosophy 30:187–209.
Flammarion, C. 1892. La planète Mars et ses conditions d’habitabilité [volume 1]. Paris: Gauthier-Villars et Fils.
Grotzinger, J.P. and Knoll, A.H. 1995. Anomalous carbonate precipitates: is the Precambrian the key to the Permian? PALAIOS 10:578–596.
Lapôtre, M.G.A., O’Rourke, J.G., et al. 2020. Probing space to understand Earth. Nature Reivews Earth and Environment 1:170–181. https://doi.org/10.1038/s43017-020-0029-y.
Lapôtre, M.G.A., Bishop, J.L., et al. 2022. Mars as a time machine to Precambrian Earth. Journal of the Geological Society 179. https://doi.org/10.1144/jgs2022-047.
Lowell, P. 1906. Mars and its Canals. New York: Macmillan.
Lowell, P. 1908. Mars as the Abode of Life. New York: Macmillan.
Sautery, B., Charnay, B., et al. 2022. Early Mars habitability and global cooling by H2-based methanogens. Nature Astronomy 6:1263–1271. https://doi.org/10.1038/s41550-022-01786-w.
Wallace, A.R. 1907. Is Mars Inhabited? New York: Macmillan.
For more on Mars and its Canals, see:
Sheehan, W. 1997. The Planet Mars: A History of Observation and Discovery. Tuscon: The University of Arizona Press. [This is a very readable overview of the history of Martian observation, interpretation, and exploration. For the canal business, see Chapters 5–9, and see especially Chapter 7 on Lowell.]
Gould, S.J. 1998. War of the worldviews. In Leonardo’s Mountain of Clams and the Diet of Worms, 339–354.
This essay from The Public Domain Review.
This article on Giovanni Schiaparelli.
And here is a 1994 documentary on the Lowell Observatory narrated by Captain Jean-Luc Picard himself.