Plate Tectonics on Mars -- a Make or Break for Life?

Olympus Mons, Mars. 70,000 ft. tall.

By Douglas Watts

SUMMARY: Most recent (2017) data indicates that while Mars had some plate tectonics around 3.5 billion years ago, it has not had any since then. While the jury is still out on whether Mars ever had or still has life, evidence seems unequivocal that Mars has not had plate tectonics like Earth for the past 3.5 billion years. Mars' crust seems to be as frozen-in-place as the Moon (and has been for 3.5 GY). Venus still has active volcanism; Earth still has active volcanism and plate tectonics. Mars does not.

For Mars, two separate issues are invoked (life; plate tectonics). Are they connected? Like Venus, Mars today has 'nowhere to go' -- its atmosphere and surface rock are in chemical, pressure and temperature equilibrium [Venus can't get cooler; Mars can't get warmer]. For Venus and Mars to be terraformed to Earth-like conditions, Venus must lose 80 percent of its atmosphere. Mars must increase its atmosphere proportionally (from 6 mbar to 700-1000 mbar). Absent giant asteroid collisions or displacements of orbital distance from the Sun, Venus and Mars appear stuck forever in their present atmospheric density, temperature and chemistry equilibria. These conditions prohibit all known life.

Two Mars features (Olympus Mons; Valles Marineris) strongly suggest the crust of Mars has been locked in place for 3+ billion years. If Olympus Mons (a classic 'hot spot' mantle volcano) was at the position of Hawaii, it would have travelled 1,500+ miles in the last 100 million years (ie. similar to Hawaii to Midway). It hasn't moved a foot. Craters on the caldera show this.

The lack of crustal movement on Mars for + 3GY is not per se prohibitive of life. But it does suggest Mars has very little heat in its crust and upper mantle. And unlike Venus, Mars is not suffering from a super-abundance of heat. On a Mars summer day (when temps. are near 70 F), at sundown it drops to -94 F. This is lower than the lowest temperature ever measured on Earth outside the Antarctic Ice Plateau (Snag, Yukon Territory, Canada at -81 F). On a cold winter night on Mars the temperature hits -216 F (the freezing point of carbon dioxide is -113 F). On a hot summer night at Mars' equator the temperature is lower than almost anywhere ever recorded on Earth.

While Mars and Earth are sometimes considered 'similar' planets -- Mars is actually more like the Moon. It's just too small to be like Earth. Mars has 1/2 the diameter of Earth, 1/6th the volume, and 1/9th the mass. Six Mars (by volume) can fit in Earth; nine Mars by mass. The ratio of surface area to volume on Mars is twice that of Earth. This means that Mars' internal heat leaks out to space twice as fast as Earth. This is a nasty conundrum since Mars started 4.5 GY ago with 11 percent of the original heat of the Earth but has been losing its heat into space twice as fast [think of a balloon or a bucket; one is 6X smaller than the other but losing its water twice as fast; which will empty faster over 4 billion years?]

The Universe is a Really, Really, Cold, Dark and Empty Place.

If you set your 'Star Trek' transporter at random, your chances of being transported to a place not at absolute zero and less than a million billion miles from the nearest warm spot would be like winning Powerball two weeks in a row. The weird thing about temperature is that its low point is bounded (absolute zero); its high point has no proportional boundaries (how about 10 million degrees !!!). Earth (and liquid water) is at the low end of the scale.

Planets have a tough time. They coalesce at 1-3,000 F but then start cooling off, like horseshoes taken out of a blacksmith's foundry. The outside atmosphere is not 40 F, but absolute zero. Radioactive decay (Uranium and Thorium) gives them some 'built-in' heat which is very slowly given off (half life of U-238 = 4.5 GY). But Mars has only 1/6th to 1/9th the 'bank account' of U/Th as Earth and sheds the heat from its U/Th bank account twice as fast. So how do planets create (and hold) their natal heat?

Tides. Jupiter's inner moon, Io, is the most volcanically active planetoid in the Solar System. Its heat source is from being pulled and tugged relentlessly by Jupiter (and its sister moons around Jupiter). Tidal friction is enough to cause a planetoid to swell, shrink and grind against itself every few days, weeks and months and generate heat friction sufficient to melt rock and make volcanoes. Venus is not as tidally heated as Io, but its ambient temp. (900F) is so high its rocks are ready to flow like thick honey with just a polite suggestion. Why is Mercury not like this? It has no atmosphere and no green house gasses to trap and keep its heat. Any potter understands it is not enough to get a temperature up to 1200 F for a few minutes; to make rock melt and flow the melting temperature must be kept up for long periods (this is called 'heat work'). This is sort of like microwaving a turkey so its skin is charred but its center is still frozen; and why in the Arctic there is 1,000 feet of permafrost below 10 feet of thawed soil on the surface. The heat-budgets (and heat budget histories) of planets and planetoids are not well understood. Since the initial seismograph on Viking 1 failed in 1976, there is still no useful seismology for Mars.

Sagan and the Drake Equation

The inference that 'some' planets in Milky Way 'must' support life (by random chance) is easily testable via exercises such as Powerball drawings. Odds of winning Powerball this week are ~ 1: 292 million. In Fall 2017, there were 21 Powerball drawings in a row without a winner. The minimum time for planets to form and cool enough to support life is at the 1-2 GY scale. At Powerball odds, a galaxy like the Milky Way could stochastically go billions of years without hitting a "Powerball winner," ie. a planet supporting life of any type (and especially, complex multicellular life).

The maximum age of the visible Universe is approx. 13.8 GY, with conditions possibly supporting life occuring at its half way point or later. (7 GY). This leaves scant room for the creation of life (most, if not all life had to have developed since 7GY when the Universe cooled down and formed stable galaxies and Sun-type, middle sequence stars). As such, a Sagan-Drake inference that there must be some planets with life somewhere would be a much better bet if the visible Universe was 130, 1300, 13,000 or 130,000 GY, in the same sense that multi-cellular life is much more probable if the Earth's age is 4.5 GY than 1 GY.

But What About Us?

Then how the Hell are we here? Good question. Maybe Earth is the first planet to support life (and multi-cellular life) in the Milky Way. Even in a race where everyone tries to lose, someone has to come in first. To take Darwinism on its face, there is no reason, impetus, cause, direction or desire for what we call *life* to evolve in the first place. Rocks and clay appear quite content just being what they are for billions and billions of years. Just as life has no direction toward complexity, the Universe has no direction toward life.

But What About Antarctic Meteorites?

Of the millions of meteorites which have landed on the Antarctic Ice Plateau in the past 20,000 years from Outer Space, one would think that one of them contained tiny bits of life adapted to live in an environment of ice and very low temperature and would form a 'colony' near the impact site. But none have. If Galactic life is highly fungible (in terms of tolerance to extremes of climate, atmosphere, temperature), then surely Earth's constant bombardment by meteorites over millions of years should have produced one viable 'seed.'

Plate Tectonics: The Forgotten Revolution

It's now hard to recall how bitterly the concept of Plate Tectonics was opposed during the 20th century.  I still have geology textbooks and stacks of professional papers from the 1960s and 1970s which grudgingly concede that plate tectonics 'could' be 'possibly' true (John McPhee's book, 'In Suspect Terrane' interviews one of the last dead-enders). Today, these books read like someone saying that since it has not yet been proven that mice do not spontaneously generate from pile of rags in the cellar, we must assume they might. Thankfully there was Apollo 11. On July 20, 1969, in one hour of specimen collection, Astronaut Neil Armstrong collected 20 pounds of Moon rocks and turned 1 million+ pounds of geology tomes into paper suited only for re-pulping. [Apollo geologist/astronaut Harrison Schmitt said of Armstrong, "Until Apollo 17 we really did not get very much good, solid descriptive work, with one exception -- Neil Armstrong. He was probably the best observer we sent to the Moon; in spite of very limited training, he just had a knack for it."]

It is not coincidental that the plate tectonics revolution of the late 1960s on Earth coincided with humans' first exploration of planets outside Earth. Absent plate tectonics, no sense could be made of the Moon (or Mars or Venus) any more than reaching the Moon via rocket at 25,000 mph could be done if it was still assumed the Earth could be the Center of the Universe and the jury was still out on Kepler and Newton. [cf. Michael Collins, 7/20/1969 to Houston: "The accuracy of the system is phenomenal. Out of a total of nearly 3,000 feet per second, we have velocity errors in our body axis coordinate system of only 1/10th foot per second in each three directions."]

Exoplanets Fuse Harmoniously Geology, Biology and Physics.

For a biologist, studying Venus seems like a giant, expensive waste of time (why not study molten lead?). But for studying the prospect of life on exo-planets, Venus is incredibly important. Venus offers the only example of what can happen when an Earth-sized planet is a bit too close to its star (and how far a 'bit' might be). For geologists, Mars offers a similar and singular example: what happens when a planet never develops plate tectonics, but all other normal activities (mantle hot spots) are intact? I think this is what folks like Neil Armstrong, Jim Lovell and Bill Anders hoped might eventually happen when they went up into the tin-cans called Apollo 8 and 11. I think they hoped that their explorations would cause the over-specialized branches of geology, astronomy, biology, physics and materials engineering (not to mention computers) to come back together. This is not unheard of. Walking up the Sheepscot River in Palermo, Maine on a rainy cold day in November, I saw a pair of 70-foot pine trees which began as separate trunks join and fused 20 feet up into one trunk, then split off again at 40 feet. It shook me. For those 20 feet, the two pine trees were living and working as one tree.