Why Did Mars Die? - Unveiling Its Geological Mystery

[aquitaine]

I've kind of been wondering that, we know that it used to have an ocean and we also know, based on mountains like Olympus Mons that it used to have an active core. That core is now dead, but why?

 

[russ_watters]

Planets cool.

 

[D H]

We don't know that either is the case. Whether Mars once had oceans, as opposed to little patches of open water, remains conjectural. There are signs that Mars once was wet and once had an active core, but there are no signs that Mars developed plate tectonics (Olympus Mons is one of those signs).

Why Mars' core became inactive is fairly simple: Mars is too small. Compared to the Earth, Mars' small size means that the formation of Mars generated a lot less gravitational heating than did the formation of the Earth (it had less enthalpy to begin with) and it means that Mars cooled a lot faster than did the Earth (temperature loss is roughly inversely proportional to mass).

The Earth's core will become dead eventually, too. It is dying now; the Earth's inner core is solid. Eventually enough of the Earth's outer core will freeze and the Earth too will become lifeless. This will happen long before the Sun turns into a red giant, but a long long time from now.

 

[Chronos]

The problem with Mars is its core. It never had enough iron-nickel to generate an earth-like magnetic field. Lacking a sufficient magnetosphere, the solar wind stripped away the martian atmosphere after about a billion years. Unlike women, planets cannot retain water without an atmosphere. The relatively low mass of Mars accelerated the process, as D H noted.

 

[aquitaine]

We don't know that either is the case. Whether Mars once had oceans, as opposed to little patches of open water, remains conjectural. There are signs that Mars once was wet and once had an active core, but there are no signs that Mars developed plate tectonics (Olympus Mons is one of those signs).

Why Mars' core became inactive is fairly simple: Mars is too small. Compared to the Earth, Mars' small size means that the formation of Mars generated a lot less gravitational heating than did the formation of the Earth (it had less enthalpy to begin with) and it means that Mars cooled a lot faster than did the Earth (temperature loss is roughly inversely proportional to mass).

The Earth's core will become dead eventually, too. It is dying now; the Earth's inner core is solid. Eventually enough of the Earth's outer core will freeze and the Earth too will become lifeless. This will happen long before the Sun turns into a red giant, but a long long time from now.

Interesting, but how long is a long long time? A few hundred million years?

 

[baywax]

I've kind of been wondering that, we know that it used to have an ocean and we also know, based on mountains like Olympus Mons that it used to have an active core. That core is now dead, but why?

Here's some of the latest on what events shaped mars...

On June 25, 2008, three teams of astronomers announced the publication of separate papers in the June 26, 2008 edition of Nature supporting the hypothesis that Mars has the largest known impact structure (Borealis Basin) in the Solar System, supplanting the Aitken Basin at the Lunar South Pole. First proposed in 1984, the massive elliptical depression in Mars northern hemisphere is partially obscured by the volcanic lava flows of the Tharsis Bulge. It was created by an impact with an object up to over half the size of planet Mercury (between one-tenth and two-thirds the size of Earth's Moon) around 4.4 billion years ago, within 200 million years of planet Mars' formation. Creating a crater four times larger than any other confirmed in the Solar System (around 8,520 by 10,650 kilometers or 5,294 by 6,618 miles across), the impact stripped off 40 percent of Mars' crust and left a surface that is lower, smoother, and less marked by craters than that found in its southern hemisphere (NASA MRO news release; Ashley Yeager, Science News, June 25, 2008; David Shiga, New Scientist, June 25, 2008; Katherine Sanderson, Nature News, June 25, 2008; Andrews-Hanna et al, 2008; and Wilhelms and Squyres, 1984).

and with regard to oceans on mars...

Breaking News

A great ocean once covered slightly over a third of the Martian surface some 3.5 billion years ago, according to a new study by scientists at the University of Colorado in Boulder (CU-Boulder). Although previous studies had proposed the existence of a large, ancient ocean on Mars over the past two decades, the available evidence was repeatedly contested. This new study provides further support for the idea of a sustained sea on the Red Planet within and along the margins of the northern lowlands during Mars' wet and warm Noachan epoch (around 4.1 billion to 3.7 billion years ago), based on global databases of known river delta deposits, valley networks, and present-day Martian topography. In a related study, scientists also detected roughly 40,000 river valleys on Mars, around four times the number of river valleys previously identified. These new findings also support the hypothesis that an ocean formed on early Mars as part of a global and active hydrosphere. The ancient ocean likely covered about 36 percent of the planet and contained around 30 million cubic miles, or 124 million cubic kilometers, of water (the equivalent of a 1,800-foot, or 550-meter-deep layer of water spread out over the entire planet, but still about 10 times less than the current volume of Earth's oceans). (CU-Boulder press releases of June 13, 2010; June 17, 2009; and Di Achille and Hynek, 2010).

all quotes from

http://www.nova.org/~sol/solcom/stars/mars.htm

 

[Orion1]

'Why did Mars die?' may be the wrong question. All the planets in the solar system and discovered around other stars are basically 'dead planets', except the Earth. The term 'dead planet' may itself be a highly subjective term given the extreme conditions that life itself may occur in the Universe. Unless the topic is strictly a discussion about active geological processes such as volcanism and surface erosion.

Mars itself during its formation may have formed a closer orbit to the sun than it is today and more inside the 'habitable zone' for the sun, with a much denser atmosphere and a much warmer surface. As a result of perturbative orbital resonances from Jupiter, resulted in its present orbit with the sun beyond the habitable zone.

The martian moons, Phobos and Deimos did not form naturally with the planet, but are actually captured asteroids from the Ceres asteroid belt located between Mars and Jupiter. A planet did not form there also as a result of perturbative orbital resonances from Jupiter.

The large amount of excavation and deposition that has occurred on Mars was definitely the result of a large liquid ocean on Mars and precipitation such as rainfall.

Mars internal core being much smaller than Earth's, cooled much more rapidly resulting in the decay of its magnetic field resulting in its atmosphere being subjected to solar radiation and the solar wind which dissipated most of the atmosphere including most of its precipitation into space. Mars primitive liquid ocean probably only lasted for a billion years. It is also probable that Venus once had a primitive liquid ocean also for the same amount of time.

Liquid water cannot exist on the surface of Mars due to its low atmospheric pressure, except at the lowest elevations for short periods. However, the two polar ice caps appear to be made largely of water. The volume of water ice in the south polar ice cap, if melted, would be sufficient to cover the entire planetary surface to a depth of 11 m.

Mars primitive ocean would not have been as deep as that of Earth's, however was sufficient enough to account for the extensive excavations and depositions and precipitation on Mars.

An excellent detailed map of Mars is available for exploration through Google Earth software, I highly recommend it.
[/Color]
Reference:
http://en.wikipedia.org/wiki/Mars#Hydrology"
http://earth.google.com/"

 

[baywax]

'Why did Mars die?' may be the wrong question. All the planets in the solar system and discovered around other stars are basically 'dead planets', except the Earth. The term 'dead planet' may itself be a highly subjective term given the extreme conditions that life itself may occur in the Universe. Unless the topic is strictly a discussion about active geological processes such as volcanism and surface erosion.

Mars itself during its formation may have formed a closer orbit to the sun than it is today and more inside the 'habitable zone' for the sun, with a much denser atmosphere and a much warmer surface. As a result of perturbative orbital resonances from Jupiter, resulted in its present orbit with the sun beyond the habitable zone.

The martian moons, Phobos and Deimos did not form naturally with the planet, but are actually captured asteroids from the Ceres asteroid belt located between Mars and Jupiter. A planet did not form there also as a result of perturbative orbital resonances from Jupiter.

The large amount of excavation and deposition that has occurred on Mars was definitely the result of a large liquid ocean on Mars and precipitation such as rainfall.

Mars internal core being much smaller than Earth's, cooled much more rapidly resulting in the decay of its magnetic field resulting in its atmosphere being subjected to solar radiation and the solar wind which dissipated most of the atmosphere including most of its precipitation into space. Mars primitive liquid ocean probably only lasted for a billion years. It is also probable that Venus once had a primitive liquid ocean also for the same amount of time.



Mars primitive ocean would not have been as deep as that of Earth's, however was sufficient enough to account for the extensive excavations and depositions and precipitation on Mars.

An excellent detailed map of Mars is available for exploration through Google Earth software, I highly recommend it.
[/Color]
Reference:
http://en.wikipedia.org/wiki/Mars#Hydrology"
http://earth.google.com/"

Orion1, would an impact as has been described above have some effect on the development and efficiency of the planet's core.. over time...?

 

[Orion1]

Mars potential appearance during the Noachan epoch

Tharsis Bulge ... It was created by an impact with an object up to over half the size of planet Mercury (between one-tenth and two-thirds the size of Earth's Moon) around 4.4 billion years ago, within 200 million years of planet Mars' formation.

The impact stripped off 40 percent of Mars' crust and left a surface that is lower, smoother, and less marked by craters than that found in its southern hemisphere.

Orion1, would an impact as has been described above have some effect on the development and efficiency of the planet's core.. over time...?

If the martian impactor formed in one of the Lagrangian points of Mars, it would be expected to have similar composition to Mars or the Ceres asteroids. The impactor's core would have sank into Mars core, enriching the core with radioactive Iron and Nickel and increasing its total size and resulting in an increase in core radioactivity and core decay lifetime and a sharp spike in Mars magnetic field that would have been magnetically recorded in the cooling basaltic magma in the Borealis Basin as opposed to crustal material which cooled during earlier or later martian epochs.

Other physical effects also include an increase in total angular momentum of the Mars-Phobos-Deimos system.

40 percent of Mars' crust ejected into Mars' orbit as an orbiting ring of debris would have quickly coalesced into a highly rounded molten basaltic sphere and quickly cooled into a highly rounded basaltic moon within less than a month, but in no more than a century.

A rough calculation of the amount of basaltic material ejected into Mars orbit from the impactor:
m = f \rho_b dV = f 4 \pi \rho_b R^2_{\circ} dr

Key:
f = 0.4 - fraction of crustal material ejected into an orbiting ring of debris
\rho_b = 3 \cdot 10^3 \; \frac{\text{kg}}{\text{m}^3} - Basalt density
R_{\circ} = 3396.2 \cdot 10^3 \; \text{m} - Mars radius
dr = 50 \cdot 10^3 \; \text{m} - Mars crust thickness

Mass of basaltic material ejected into Mars orbit from the impactor:
\boxed{m = 8.697 \cdot 10^{21} \; \text{kg}}

The masses of Phobos and Deimos:
m_1 = 1.072 \cdot 10^{16} \; \text{kg} - Phobos mass
m_2 = 1.48 \cdot 10^{15} \; \text{kg} - Deimos mass

Although I am not aware of any theory that suggests that Phobos and Deimos were blasted from Mars' surface into orbit as opposed to being captured objects from the Ceres asteroid belt or Mars' Lagrangian locations.

There also seems to be a similar geologic chronology between the Theia-Terra impact theory and the impactor-Mars theory:

4.53 to 4.6 billion years ago - Theia-Terra theory
4.4 billion years ago - impactor-Mars theory

Which may indicate that dwarf planets, rogue moons and asteroids debree may be a common formation in the Lagrangian points of planets during planetary formation which inevitably impact the primary orbiting proto-planet via gravitational perturbations from stable Lagrangian locations.
[/Color]
Reference:
http://wiki.answers.com/Q/Density_of_basalt"
http://www.nasa.gov/worldbook/mars_worldbook.html"
http://en.wikipedia.org/wiki/Giant_impact_hypothesis#Theia"
http://en.wikipedia.org/wiki/Mars#Impact_topography"
http://en.wikipedia.org/wiki/Phobos_%28moon%29"
http://en.wikipedia.org/wiki/Deimos_%28moon%29"
http://en.wikipedia.org/wiki/Lagrangian_point"

 

[Naty1]

the solar wind stripped away the martian atmosphere after about a billion years

That's the explanation I have read, but the items posted above are really insightful...

 

[Chronos]

Moons are quite uncommon among the inner planets. Only Earth has a moon of more than token size, and it is clearly a freak. Mars has these laughable excuses for moons that, IMO, were almost surely captured from the nearby asteroid belt. Jupiter and Saturn have the lions share, most of which are probably remnants of their original accretion discs. Neptune and Uranus as well, although to a lesser extent.

The stripping of the martian atmosphere after a billion years is, again IMO, fascinating. That is just about the same time we have evidence of life arising on earth. I think it is probable Mars also evolved abiogenic life forms given conditions in martian oceans should have been very similar to those on Earth around deep sea volcanic vents.

 

[baywax]

Mars potential appearance during the Noachan epoch





If the martian impactor formed in one of the Lagrangian points of Mars, it would be expected to have similar composition to Mars or the Ceres asteroids. The impactor's core would have sank into Mars core, enriching the core with radioactive Iron and Nickel and increasing its total size and resulting in an increase in core radioactivity and core decay lifetime and a sharp spike in Mars magnetic field that would have been magnetically recorded in the cooling basaltic magma in the Borealis Basin as opposed to crustal material which cooled during earlier or later martian epochs.

Other physical effects also include an increase in total angular momentum of the Mars-Phobos-Deimos system.

40 percent of Mars' crust ejected into Mars' orbit as an orbiting ring of debris would have quickly coalesced into a highly rounded molten basaltic sphere and quickly cooled into a highly rounded basaltic moon within less than a month, but in no more than a century.

A rough calculation of the amount of basaltic material ejected into Mars orbit from the impactor:
m = f \rho_b dV = f 4 \pi \rho_b R^2_{\circ} dr

Key:
f = 0.4 - fraction of crustal material ejected into an orbiting ring of debris
\rho_b = 3 \cdot 10^3 \; \frac{\text{kg}}{\text{m}^3} - Basalt density
R_{\circ} = 3396.2 \cdot 10^3 \; \text{m} - Mars radius
dr = 50 \cdot 10^3 \; \text{m} - Mars crust thickness

Mass of basaltic material ejected into Mars orbit from the impactor:
\boxed{m = 8.697 \cdot 10^{21} \; \text{kg}}

The masses of Phobos and Deimos:
m_1 = 1.072 \cdot 10^{16} \; \text{kg} - Phobos mass
m_2 = 1.48 \cdot 10^{15} \; \text{kg} - Deimos mass

Although I am not aware of any theory that suggests that Phobos and Deimos were blasted from Mars' surface into orbit as opposed to being captured objects from the Ceres asteroid belt or Mars' Lagrangian locations.

There also seems to be a similar geologic chronology between the Theia-Terra impact theory and the impactor-Mars theory:

4.53 to 4.6 billion years ago - Theia-Terra theory
4.4 billion years ago - impactor-Mars theory

Which may indicate that dwarf planets, rogue moons and asteroids debree may be a common formation in the Lagrangian points of planets during planetary formation which inevitably impact the primary orbiting proto-planet via gravitational perturbations from stable Lagrangian locations.
[/Color]
Reference:
http://wiki.answers.com/Q/Density_of_basalt"
http://www.nasa.gov/worldbook/mars_worldbook.html"
http://en.wikipedia.org/wiki/Giant_impact_hypothesis#Theia"
http://en.wikipedia.org/wiki/Mars#Impact_topography"
http://en.wikipedia.org/wiki/Phobos_%28moon%29"
http://en.wikipedia.org/wiki/Deimos_%28moon%29"
http://en.wikipedia.org/wiki/Lagrangian_point"

Very cool Orion1! The impact, which apparently did penetrate Mar's core, would then have set a course for an early demise of the magnetic field and the gravitational strength of the planet. This would lead to its atmosphere being easily stripped away by cosmic winds.

Outstanding correlations!

It may be that Phobos and Deimos did originate from the crust of Mars. The debris could still be considered as "captured" in that it did not escape the confines of Martian gravity. As you say, it could have been a month to within a century for the debris to form two "moons".

Call me crazy but I've always figured the impact was more recent than 4.6 billion years ago... I'm thinking more like recent pre-history. My only evidence comes from oral tradition stories of different firstnations. These and the fact that the word "mar" can mean "sea" and to have someone name Mars after an ocean would mean they'd seen it with oceans on it... but these are far fetched ideas that are not readily provable. The closest I've come to matching the linguistics to "mar" is an ancient Turkish word "mar" or "mer" which means "rebellious" and "unruly", which an ocean can be... and which applies to a planet of "war". Also, if the impact had been witnessed by earlier humans they might end up calling the planet "the god of war"... what with all the fireworks.

 

[baywax]

Here's a photo showing evidence of a massive impact on mars...

Fri Aug 6, 11:05 AM
Denise Chow
SPACE.com Staff Writer
SPACE.com

A striking bull's-eye on Mars - evidence of another massive Martian impact - has been beamed to Earth from the high-powered camera onboard a powerful NASA spacecraft orbiting the red planet.

The photo of the unusual-looking crater was taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter. [Mars bull's-eye crater photo]

Scientists are now trying to determine what could have caused the central pit within the Mars impact crater. In other words, was it the product of unusual subsurface layering, or was it created by a fortuitous second impact?

http://ca.news.yahoo.com/s/yahoocanada/mysterious_bull_s_eye_on_mars_revealed;_ylt=ApokRwFYc6GnPa9dT6FMlSV4l80F

 

[Orion1]

Mars moons Phobos (left) and Deimos (right).

Mars has two tiny natural moons, Phobos and Deimos, which orbit very close to the planet. Their known composition suggests the moons are captured asteroids but their origin remains uncertain. The origin of the two moons is not well understood.

Their low albedo and carbonaceous chondrite composition are similar to asteroids and capture remains the favored theory. The unstable orbit of Phobos would seem to point towards a relatively recent capture.

But both have circular orbits, very near the equator, which is very unusual for captured objects and the required capture dynamics are complex. Accretion early in the history of Mars is also plausible but does not account for the moons' composition resembling asteroids rather than Mars itself.

A third possibility is the involvement of a third body or some kind of impact disruption.

The main asteroid belt (shown in white) is located between the orbits of Mars and Jupiter.

Mars has these... moons that, IMO, were almost surely captured from the nearby asteroid belt. Jupiter and Saturn have the lions share, most of which are probably remnants of their original accretion discs.

In order for a planet's original accretion disc to even form an appreciable mass sized moon, barring the Earth-Lunar and Pluto-Charon systems exceptions, requires a minimum mass of a gas giant planet greater than or equal to at minimum the mass of Uranus.

Minimum mass for planet's original accretion disc to form a moon (Uranus mass):
\boxed{M_{\circ} \geq 8.6810 \cdot 10^{25} \; \text{kg}}
[/Color]
Reference:
http://en.wikipedia.org/wiki/Mars#Moons"
http://en.wikipedia.org/wiki/Asteroid_belt"
http://en.wikipedia.org/wiki/Uranus"

 

[baywax]

Excellent work Orion1. There are a myriad of possibilities with regard to the age and origin of mar's moons, the age of the larger impact and so on... there really has to be a fact finding probe or 6 put out there to clarify the timelines of these events.

 

[qraal]

All possibilities. Hard data is hard to come by to ever really know.

Personally I think the idea that our Moon and others were captured from solar orbit is still a goer. But I'll leave that as a teaser for later discussion. Nice work guys.

 

[Orion1]

How did the Earth live?


'Why did Mars die?' may be the wrong question. All the planets in the solar system and discovered around other stars are basically 'dead planets', except the Earth. The correct question may be given the natural hostility of star system environments forming from a stellar accretion disc is, how the Earth was able to survive with a surface ecosystem and life for such a long duration of time?

Mars moons Phobos (left) and Deimos (right).

253 Mathilde, a C-type asteroid

The Phobos and Deimos low albedo and carbonaceous chondrite composition are similar to asteroids and capture remains the favored theory. The unstable orbit of Phobos would seem to point towards a relatively recent capture.

C-type asteroids are carbonaceous asteroids. They are the most common variety forming around 75% of known asteroids, and an even higher percentage in the outer part of the belt beyond 2.7 AU, which is dominated by this asteroid type. The proportion of C-types may actually be greater than this, because C-types are much darker than most other asteroid types except D-types and others common only at the extreme outer edge of the Main Belt.

C-type asteroids are extremely dark with albedos typically in the 0.03 to 0.10 range

If Phobos and Deimos are captured objects from the Ceres asteroid belt, then their age is around 4.6 billion years old.
[/Color]
Reference:
http://en.wikipedia.org/wiki/Asteroid_belt"
http://en.wikipedia.org/wiki/C-type_asteroid"
http://en.wikipedia.org/wiki/Solar_System#Formation_and_evolution"

 

[baywax]

Mars Impact Hypothesis

"We haven't proved the giant-impact hypothesis, but I think we've shifted the tide," said Jeffrey Andrews-Hanna, a postdoctoral researcher at the Massachusetts Institute of Technology in Cambridge.

NASA's Mars Reconnaissance Orbiter and Mars Global Surveyor have provided detailed information about the elevations and gravity of the Red Planet's northern and southern hemispheres. A new study using this information may solve one of the biggest remaining mysteries in the solar system: Why does Mars have two strikingly different kinds of terrain in its northern and southern hemispheres? The huge crater is creating intense scientific interest.

The mystery of the two-faced nature of Mars has perplexed scientists since the first comprehensive images of the surface were beamed home by NASA spacecraft in the 1970s. A giant northern basin that covers about 40 percent of Mars' surface, sometimes called the Borealis basin, is the remains of a colossal impact early in the solar system's formation, the new analysis suggests. At 8,500 kilometers (5,300 miles) across, it is about four times wider than the next-biggest impact basin known, the Hellas basin on southern Mars. An accompanying report calculates that the impacting object that produced the Borealis basin must have been about 2,000 kilometers (1,200 miles) across.

That's larger than Pluto. The impact gouged out a crater the size of the combined areas of Asia, Europe and Australia, researchers reported in the journal Nature. It appears to have held an ocean in the early days of the planet, before Mars lost so much of its atmosphere and the water either sublimated away or froze beneath the surface.

"This is an impressive result that has implications not only for the evolution of early Mars, but also for early Earth's formation," said Michael Meyer, the Mars chief scientist at NASA Headquarters in Washington. When the solar system was just maturing 4 billion years ago, big objects often smashed into one another. The formation of the Earth's Moon is attributed to a giant impact on the Earth by a Mars-sized body.

more: http://www.dailygalaxy.com/my_weblog/2009/03/mars-discovery.html

I'm not a crater morphologist but the craters that seem to have "fortuitously" been created dead center at the center of the impact shown in the above photo appear to be pretty young in age.