Media and Journals Conflict Over Mars Life
Timed for the one-year anniversary of the Mars Exploration Rovers, PBS aired a NOVA program last night about Spirit and Opportunity, and the teams that landed them and operated them on Mars. As is common for popular programs about Mars exploration, NOVA suggested that evidence for past water found (especially by Opportunity at Meridiani Planum) means that life may have existed there. As support, the program pointed to all the hostile places on Earth where life has been discovered.
By contrast, very negative conclusions about life on Mars were announced in the Journal of Geophysical Research: Planets1 by Dawn Y. Sumner, geologist at UC Davis. Her paper claims the mineralogy makes life very unlikely:
Life is composed of organic compounds, and characterizing preserved compounds provides insights into the presence of specific types of life, including early life on Earth. With growing evidence for a wet early Mars, excitement over the potential of an early Martian biosphere strongly motivates Mars exploration. However, the preservation potential of organic compounds in rocks on either Earth or Mars depends critically on mineralogy. Results from elemental, mineralogical, and morphological characterization of sedimentary rocks by the Opportunity rover team in the vicinity of the Challenger Memorial Station, Meridiani Planum, demonstrate an abundance of Fe(III) and sulfate minerals that formed from liquid water. The composition of these sedimentary rocks suggests that organic compounds are unlikely to be preserved within them, even if present when the rocks were deposited, based on comparisons with iron formation, acid lake deposits, and iron-containing concretions from Earth. No evidence consistent with the presence of organic compounds, such as the presence of Fe(II) minerals, has been reported from Meridiani Planum to date. Thus these Martian sedimentary rocks are not a good target to explore for organic compounds on Mars. (Emphasis added in all quotes.)
The poor potential for preservation of organics does not preclude the past existence of life, but the problem is that organics would have oxidized under the conditions that laid down the rocks. For instance, the NOVA program made a big deal about the hematite and jarosite being evidence of water, but Sumner states, “Note that in the presence of hematite and jarosite, organics are not thermodynamically stable.” If life is composed of organic molecules, it would seem conditions were hostile to life even during the past wet periods. This has implications for the search for life on Mars, she concludes:
Exploring for complex organic compounds with an in situ mission to Meridiani Planum unit P2 sedimentary rocks is not likely to produce positive results given the absence of mineralogical evidence for good organic preservation and the abundance of evidence for minerals inimical to long-term preservation. At best, organics will be difficult to find and, if not found, their absence can be attributed to the low preservation potential of the host rocks. Results will not allow us to distinguish between an initial absence of organics and an absence due to poor preservation. Thus, in situ organic compound characterization of these rocks is unlikely to contribute to the goal to “Determine if Life Ever Arose on Mars.”
A sample return mission would provide better resolution, but looking at another spot is her recommendation.
1Dawn Y. Sumner, “Poor preservation potential of organics in Meridiani Planum hematite-bearing sedimentary rocks,” JGR Planets, Journal of Geophysical Research, Vol. 109, E12007, doi:10.1029/2004JE002321, 2004.
Do you get angry when TV shows ignore these facts? Science programs on secular TV routinely gloss over major difficulties with evolutionary myths, and make the origin of life seem as simple as “just add water.” The NOVA program was commendable for its portrayal of the human drama of exploration, and the MER team deserves credit for the tremendous technological feat they accomplished, and the enthusiasm and dedication with which they carried it out. But they did not help the search for life: in fact, the results have been depressing compared to earlier expectations (see 12/20/2004, 12/03/2004, 10/18/2004, 08/06/2004 headlines). They found evidence that Mars had wet periods, at least intermittent shallow ones sometime in the past. But water is the easy part. H2O is abundant in the solar system, and to get it in liquid form only requires an environment between its freezing and boiling points. Despite its importance and unusual properties, water is a simple molecule. It only has three atoms. The simplest molecules of life involve thousands of atoms, in complex molecules hundreds of units long, interacting in complex ways. What’s more, an incipient lifeform must be able to accurately duplicate all its parts. It is the height of irresponsibility for NOVA, the Science Channel, the Discovery Channel, Bill Nye and all the other media outlets to continue to push the myth that if water is found, life cannot be far behind. If water is found, it does not mean life. If life is found, it does not mean it evolved. Extraordinary, mind-bogglingly incredible claims demand extraordinary, mind-bogglingly incredible proof.