# Why did Mars die?

1. Aug 1, 2010

### 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?

2. Aug 1, 2010

### Staff: Mentor

Planets cool.

3. Aug 1, 2010

### D H

Staff Emeritus
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.

4. Aug 1, 2010

### 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.

5. Aug 2, 2010

### aquitaine

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

6. Aug 2, 2010

### baywax

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

and with regard to oceans on mars...

all quotes from

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

7. Aug 2, 2010

### 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.

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.

Reference:
http://en.wikipedia.org/wiki/Mars#Hydrology"

Last edited by a moderator: May 4, 2017
8. Aug 2, 2010

### baywax

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

Last edited by a moderator: May 4, 2017
9. Aug 3, 2010

### Orion1

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.

Reference:
http://www.nasa.gov/worldbook/mars_worldbook.html" [Broken]
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" [Broken]
http://en.wikipedia.org/wiki/Deimos_%28moon%29" [Broken]
http://en.wikipedia.org/wiki/Lagrangian_point" [Broken]

Last edited by a moderator: May 4, 2017
10. Aug 3, 2010

### Naty1

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

11. Aug 4, 2010

### 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.

Last edited: Aug 4, 2010
12. Aug 5, 2010

### baywax

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.

Last edited by a moderator: May 4, 2017
13. Aug 7, 2010

### baywax

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

Last edited by a moderator: May 4, 2017
14. Aug 8, 2010

### Orion1

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

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

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):
$$\boxed{M_{\circ} \geq 8.6810 \cdot 10^{25} \; \text{kg}}$$

Reference:
http://en.wikipedia.org/wiki/Mars#Moons"
http://en.wikipedia.org/wiki/Asteroid_belt" [Broken]
http://en.wikipedia.org/wiki/Uranus" [Broken]

Last edited by a moderator: May 4, 2017
15. Aug 9, 2010

### 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.

16. Aug 10, 2010

### 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.

17. Aug 10, 2010

### 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

If Phobos and Deimos are captured objects from the Ceres asteroid belt, then their age is around 4.6 billion years old.

Reference:
http://en.wikipedia.org/wiki/Asteroid_belt" [Broken]
http://en.wikipedia.org/wiki/C-type_asteroid" [Broken]
http://en.wikipedia.org/wiki/Solar_System#Formation_and_evolution"

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18. Aug 11, 2010

### baywax

Mars Impact Hypothesis

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.

Last edited: Aug 11, 2010