The picture above shows seven items dubbed, “cave skylights.” They have been named the “Seven Sisters,” and respectively are clockwise from upper left are Dena, Chloe, Wendy, Annie, Abbey and Nikki, and Jeanne. (Arrows indicate direction of solar illumination [I] and north [N]).
© By Frank WarrenA research paper presented in early March at the Lunar and Planetary Science Conference in Texas, an annual get-together of experts in fields ranging from moon exploration to asteroid detection and astrobiology ignited debate about the prospect of “life” either “having existed,” or maybe even being “present now” in what are thought to be caves on a volcano named Arsia Mons near Mars' tallest mountain.
These “cave skylights,” as they have been dubbed, were discovered in images from NASA's “Mars Odyssey” spacecraft. The authors of the paper— Glen Cushing, Timothy Titus and J. Judson Wynne of the U.S. Geological Survey, in addition to Phil Christensen of Arizona State University argue, “These holes, the size of football fields may be the entrances to subterranean caverns. If the claims prove to be true, such caves would be prime targets in the search for extraterrestrial life and prime real estate for future human settlements.”
Obviously, shelter from the harsh environment of Mars, as well as “heat” from volcanic activity, in regards to “liquid water” would dramatically increase the prospects for life to exist and prosper.
Skeptics will no doubt question whether the “black spots” on the images are in fact cave, “entrances,” “skylights” or just minor “pockmarks in shadow” on the Martian surface; however, the group writes:
The Mars Odyssey Thermal Emission Imaging System (THEMIS) collected the majority of data for this study . From a nadir perspective, THEMIS observes both visible and thermalinfrared wavelengths during the afternoon (~ 1500-1700 hrs), and IR wavelengths only for early-morning observations (~ 0300-0500 hrs.) . The inspection of dark, circular pit-like features at visible wavelengths (VIS band 3, ~.654 µm) gave our first indication of potential skylight.. . . To aid in visualization, we have informally named these 'seven sisters' on Arsia Mons as: Dena, Chloë, Wendy, Annie, Abbey, Nikki and Jeanne (Figure 1). Most of the candidates are adjacent to collapse pits or are directly in-line with collapse-pit chains, and appear to have formed by similar processes. They are visibly and from an off-nadir perspective.Even if these are just “vertical shafts” in the red planet, they would still fall under the definition of a “cave” and given their size, the points raised by the researchers are still valid.
. . . If liquid water does exist at or near the surface, then caves at lower elevations could hold natural reservoirs, greatly improving the possibilities for past or present microbial life. The discovery of potential skylight openings into Martian caves is an exciting step towards future exploration and discovery. New spacecraft orbiting Mars, with greater observational capabilities, can observe these candidates at higher resolutions, at different times of day, from different perspectives and in distinct from collapse pits, however, by a lack of visible (sunlit) walls or floors. These proposed skylights also lack the visible characteristics (such as raised rims or ejecta patterns) that would associate them with impact craters. Thermal behaviors furthermore confirm they are not misidentified surface features such as dark sand or rock.
The researchers further write:
Analyses of the candidates suggest they are not of impact origin, not patches of dark surface material, and are likely skylight openings into subsurface cavernous spaces. Visible observations show dark holes with sufficient depth that no illuminated floors (incidence angles = 61.5°) can be seen from a nadir perspective (Thermal-infrared data suggest temperatures inside these features remain nearly constant throughout each diurnal cycle. . . . afternoon temperatures for Annie that are warmer than the shadows of adjacent collapse pits, and cooler than sunlit portions. Meanwhile, nighttime temperatures for this candidate are warmer than all nearby surfaces. Such is the behavior we would expect of a cavern floor that receives little or no daily solar insolation . . ..The researchers will no doubt take comfort in some “supportive evidence” found here on this planet; the features of the “Seven Sisters” are consistent with “lava tubes”; as noted by biologist Penny Boston, “the walls of collapsed lava tubes can hold deposits of permanent ice or even microbial communities.”
The one thing all agree on, is that the “Seven Sisters” deserve further analysis by superior equipment e.g., “Mars Reconnaissance Orbiter.” This orbiter offers a “higher resolution camera” and should be able to substantiate whether of not these are just “vertical shafts” or are indeed the “skylights” that open up into larger chambers.
The spacecraft is also equipped with “ground-penetrating radar” which may be able to provide a “rough map” of the caverns. Undeniably, “entering” the “caves” would be the most informative; however, a “manned mission” is still decades off in the future.
As “necessity is the mother of invention,” it will be most interesting to see what technology will be inspired by these latest findings . . . what will come of the need to explore the caves of Mars?