Within the collapse alcove of the giant Hebes Mensa salt dome on Mars, there is a feature called the "Oil Spill" (Adams et al., 2009). According to these researchers the fluid consists of liquid brines that have been coloured black by dark dust particles. However, - this cannot be true.
To me, this explanation is physically not possible. According to own earth-bound research, over the past 5 years, the most probable explanation is that the liquid substance consists of crude oil.
Earth analogue features
The current theoryThe currently published model for how the "Oil Spill" feature on Mars formed is briefly reviewed and commented below:
Adams et al. (2009) suggested that the giant Hebes Mensa salt dome structure is an "arching, emergent salt diapir". They have no good explanation on how it may have formed, nor how it links to the other features associated with it. For example, their explanation for the deep troughs surrounding the arch is: "A collapse of megaregolith by drainage of ~100.000 cubic kilometers of brines and entrained particles that drained into a regional (underground) aquifer." In other words, they want us to believe that parts of the surface of Mars surrounding Hebes Mensa (arch) dissappeared into a hole in the ground, via a dramatic washing away by water mixed with salt (brine).
Several questions to this model occur: Where did the brines come from? Where is the hole in the ground into which the water and particles dissappeared? What type of aquifer can this be, located under the Hebes Mensa and Hebes Chasma features?
Finally, we shall dwell with Adams et al's (2009) description and explanation of the "Oil Spill" feature itself. These are the exact words used on pages 692-693: "Dark fluid flows also occur on the sides of Hebes Mensa, the base of the chasma walls adjacent to the pits and troughs, and along fissures on the chasma floor. The conspicuous braided flow from the northeast alcove of Hebes Mensa here dubbed "Oil Spill" (Fig. 4C), was interpreted by Ori et al. (2005) as a low viscosity lava flow; however, a Mars Reconnaissance Orbiter Camera image shows that the braided channels are smooth ridges and that the terminal deposit has a feather edge that grades into the surrounding, paler surface. We interpret the Oil Spill as particulates (basaltic tephra?) derived from LHF [Lower Hebes Formation] and entrained in aqueous springs along fracture zones. Dark material may have accumulated in the Oil Spill channels as water evaporated."
Again, pertinent questions beg for good answers: How can an "aqueous spring" both come to surface and run down a slope making braided flow patterns? This is not possible, as you either have a spring from which the "water" emits and then runs down the slope. But, it would not be possible to have an "aqueous flow" of any kind on the surface of Mars - as the water immediately evaporates in contact with the atmosphere, even if it is salt-saturated water.
Therefore, the conspicuous braided aqueous flow on Mars is neither formed by water nor by lava. The only option is that it formed by crude oil emitting from the interior central conduits of Hebes Mensa, the collapsed giant salt dome, and flowing down the side, onto the Hebes Chasma floor.
There is one other very important observation made by Adams et al. (2009). In their Figure 2 C caption they state: "Botryoidal structures on top of Hebes Mensa resulting from fluid escape or diapirism." This means that salt-laden fluids have percolated inside the Hebes Mensa salt dome, in complete agreement with our own model of how salt domes are formed by rising brines and other material from the deep sub-surface (Hovland et al., 2011). Salt on two planets.
In the following, I will build up the model which not only explains how oil can form on Mars, but also how Hebes Mensa, and not least, the impressive Hebes Chasma may have formed, by processes that we also have on Earth.
The basis of my modelThe explanation model is based on several features and processes that also occur on Earth, although some of them are still not fully understood. The model is based on combining knowledge of
- Hydrothermal processes (underground high-temperature water-associated processes), with those of
- Serpentinization (a very important geological process on Earth and Mars),
- Salt dome formation,
- Mud volcanism,
- Supercritical water (SCRIW) transport under ground, and
- Abiotic oil formation (Fisher-Tropsh, etc).
1. Hydrothermal processesHydrothermal processes occur as a consequence of the great heat contrast between the temperature in the upper mantle and the bottom of the ocean, which is the top of the oceanic crust. The temperature gradient between these two locations can be as high as 1200 degrees C. At plate boundaries and cracks in the oceanic crust, this leads to the circulation of seawater through the curst. Thus, seawater is gradually (in some places) and rapidly (in other places) heated to extreme values. This leads to a host of different extremely important processes inside the oceanic crust. These are the hydrothermal processes, which not only affect life, minerals, and alteration of the rocks, but also lead to the precipitation of salts, formation of serpentinite, and abiotic hydrocarbons (oil or petroleum).
2. SerpentinizationSerpentinization is the process whereby water reacts with rocks in the upper mantle (peridotite) to form serpentinite. The water reacts strongly with the olivine (magnesium silicate) in the peridotite, and causes additional warming (exothermal heat), volume expansion (because of the added water to the new rock (serpentinite), and to the release of excess free hydrogen (H2).
Take a look at the results of serpentinization in the deep ocean:
"Lost City" serpentinization in action...
This process is important for three main reasons:
According to Keith et al. (2008), there is a whole sheath of serpentinite underneath most of planet Earth (and also parts of Mars). They call this sheath for the "Serpentosphere":
Beneath ocean basins and adjacent to spreading centers, oceanic Serpentosphere is continuously generated by the interactions of deep circulating marine composition water – partly in super-critical state –with harzburgitic peridotite in the process referred to as serpentinization. Conversion of the harzburgite to lizarditic serpentine under supercritical condition is texturally preservative and probably induces about 40% volume expansion. The volume expansion provides an excellent mechanism to expel and propel fluid products – including hydrocarbons – from the area of serpentinization to seep sites at the crust hydrosphere/atmosphere interface.
A downward diffusing, super-critical serpentinization front is present beneath every ocean basin and is more active where it originally formed near oceanic ridge thermal anomalies. When ocean Serpentosphere is subducted beneath continental or oceanic crust areas, it converts to antigorite-dominated serpentinite rock (generally coincident with greenschist facies metamorphism). During flat subduction, the relatively low density antigorite ‘floats’ and is underplated to the base of the continental crust at the Moho geophysical interface.
In effect, both oceanic and continental Serpentospheres reflect a deep ‘weathering’ process that consists of the interaction of deep crustal and oceanic, water-dominated fluids with the upper portion of a mainly harzburgitic peridotite at the top of the earth’s lithospheric mantle. The Serpentosphere may be viewed as a thin membrane that separates water-absent, life-free abiogenetic processes in the mantle from water-present, life-related processes above the Serpentosphere in the oceanic crust.
The Serpentosphere has enormous and novel implications for four major geologic problems that are of current interest to the geologic and social community:
1) the driving mechanism for plate tectonics,
2) the origin of life,
3) the origin of hydrocarbons, and
4)contributions to global climate.
Because the Serpentosphere has been continuously generated since the beginning of geologic time it must be considered as one of the fundamental entities of our water-surfaced planet – the only water-planet we know of ...
(Keith et al., 2008).
Serpentinization on Mars
In the conference "Serpentine Days", held during September, 2012, there were several presentations on serpentinzation on Mars: Here are some of the titles of the presentations:
- "Serpentinization on Mars, a review" (Quantin et al.)
- "Identification of serpentine between Hellas and Isidis Bassins, Mars" (Bultel et al.)
- "Primitive environment on early Mars: Relation between phyllosilicates detection and Noachian crust composition in the vicinity of Valles Marineris" (Clenet et al.).
Salt from serpentinization
As this equation (6 MgSiO3+ 4 H2O = Mg6Si4O10(OH)8+ 2 SiO2) suggests, only pure water (not the dissolved material, i.e. salts) paticipate in the reaction. this means that wherever serpentinization is going on (normally at temperatures around500 degrees C and at pressures more than 300 bars, the salt will come out of solution and has to accumulate as a very strong brine or as particulate matter. This means that there will be underground accumulation of salt. And, because of the accommodation problem below ground, it will likely stream upwards somehow, and eventually daylight at surface (on Mars) or in the ocean (on Earth), where most of it likely becomes dissolved in the seawater.
3. Salt dome formation (on Earth and Mars)
Salt domes, also called salt "diapirs" occur many places on Earth, for example in the Gulf of Mexico. To the surprize of planetary geologists, they also occur on Mars, as witnessed by Hebes Mensa. According to our model for salt dome formation, the salt domes are not only formed as salt diapirs, but also by injection of brines and solid salt particles from below ground, as part of the serpentinzation process and in hydrothermal systems. There are two main processes that form large amounts of mobile salt under ground:
1) serpentinization with seawater, and
2) circulation of seawater into spreading centres (hydrothermal cells), like in the Red Sea
Link to salt model for the Red Sea: Here
A Google Earth image of ‘Upheaval Dome’, in the Paradox Basin, Utah, USA, appears in Fig. 8. This erosive ‘Bulls eye’ feature contains anhydrite in its centre, and is suggested to represent the remains of an ancient salt dome (Mattox, 1968). Other features are also pertinent: 1) The ring-shaped rocks surrounding the anhydrite remains, in our model these represent the enclosing sediments that have surrounded the salt dome, during syn-sedimentary growth. 2) The canyon opening at the far side, which suggests that large amounts of fluids have escaped, even though the catchment area of the structure is very small. We suggest that brines have continued seeping to surface, and filled the circular structure even after it was exposed, and that saline water has eroded the canyon opening.
Internal and external pressure forces
4. Mud Volcanism
Mud volcanism is one of the strangest and least understood geological processes on Earth and Mars. A mixture of liquified minute clay particles, water (brine and pure H2O), gas (methane and carbon dioxide), and oil continuously wells up in these special volcanoes. It is only very rare that heat is associated with them, - normally they have ambient temperatures. The photo below shows a typical onshore mud volcano south of Baku, in Azerbaijan. The four components (mud, water, gas, and oil) are here present.
Mud volcanoes in the Gulf of mexico
Asphalt volcanoes in Gulf of Mexico (The Chapopote case study)
Mud volcanoes on Mars
A deep origin of mud volcanism?
5. Supercritical water
Some of the properties of SCRIW are:
There are numerous geological implications associated with SCRIW. For example it can transport dissolved oil for long distances under-ground. The oil will be deposited (as a condensate or precipitated liquid) when the SCRIW rises towards surface (is de-pressurized) or when it cools down to below about 400 oC.
SCRIW also represents the ultimate temperature and pressure barrier for normal life forms. This is because SCRIW is so "aggressive" that it dissolves all organic material. However, it does not dissolve certain salts - therefore the SCRIW phase of water is an effective salt producer from seawater.
6. Abiotic oil formation
7. Conclusions and consequences of oil on Mars
It is here suggested that there is crude oil also on Mars. Normally, it resides below ground, but occasionally will find its way to surface, either at known mud volcanoes or at breached salt diapirs.
Because oil is an "organic material" (in science, it belongs to 'organic chemistry'), it should be able to stimulate one or several of the instruments on 'Opportunity' and 'Curiosity', now roaming around on Mars.
Adams, J.B., Gillespie, A.R., Jackson, M.P.A., Montgomery, D.R., Dooley, T.P., Combe, J.-P., Schreiber, B.C., 2009. Salt tectonics and collapse of Hebes Chasma, Valles Marineris, Mars. Geology, 37 (8), 691-694
Adams et al. (2009)
Keith, S., Swan, M.M., Hovland, M., Rueslaatten, H., Johnsen, H.K., 2008. The Serpentosphere. Arizona Geological Meeting, March, 2008.
Szatmari, P., 1989. Petroleum formation by Fischer-Tropsch synsthesis in plate tectonics. AAPG Bull., 73, 989-998.