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Learning objectives

By the end of this section, you will be able to:

  • Compare the planetary evolution of Venus, Earth, and Mars

Venus , Mars , and our own planet Earth form a remarkably diverse triad of worlds. Although all three orbit in roughly the same inner zone around the Sun and all apparently started with about the same chemical mix of silicates and metals, their evolutionary paths have diverged. As a result, Venus became hot and dry, Mars became cold and dry, and only Earth ended up with what we consider a hospitable climate.

We have discussed the runaway greenhouse effect on Venus and the runaway refrigerator effect on Mars, but we do not understand exactly what started these two planets down these separate evolutionary paths. Was Earth ever in danger of a similar fate? Or might it still be diverted onto one of these paths, perhaps due to stress on the atmosphere generated by human pollutants? One of the reasons for studying Venus and Mars is to seek insight into these questions.

Some people have even suggested that if we understood the evolution of Mars and Venus better, we could possibly reverse their evolution and restore more earthlike environments. While it seems unlikely that humans could ever make either Mars or Venus into a replica of Earth, considering such possibilities is a useful part of our more general quest to understand the delicate environmental balance that distinguishes our planet from its two neighbors. In Cosmic Samples and the Origin of the Solar System , we return to the comparative study of the terrestrial planets and their divergent evolutionary histories.

Key concepts and summary

Earth, Venus, and Mars have diverged in their evolution from what may have been similar beginnings. We need to understand why if we are to protect the environment of Earth.

For further exploration

Articles

Venus

Dorminey, B. “Cool Science on a Hot World.” Astronomy (February 2006): 46. Five-page overview of Venus and the Venus Express mission plans.

Kargel, J. “Rivers of Venus.” Sky&Telescope (August 1997): 32. On lava channels.

Robertson, D. “Parched Planet.” Sky&Telescope (April 2008): 26. Overview of our understanding of the planet.

Robinson, C. “Magellan Reveals Venus.” Astronomy (February 1995): 32.

Stofan, E. “The New Face of Venus.” Sky&Telescope (August 1993): 22.

Zimmerman, R. “Taking Venus by Storm.” Astronomy (October 2008): 66. On results from the Venus Express mission.

Mars

Albee, A. “The Unearthly Landscapes of Mars.” Scientific American (June 2003): 44. Results from the Mars Global Surveyor and Mars Odyssey missions and an overview.

Bell, J. “A Fresh Look at Mars.” Astronomy (August 2015): 28. Nice summary of recent spacecraft results and how they are revising our understanding of Mars.

Bell, J. “Uncovering Mars’ Secret Past.” Sky&Telescope (July 2009): 22. How rovers and orbiters are helping us to understand Mars history and the role of water.

Bell, J. “The Red Planet’s Watery Past.” Scientific American (December 2006): 62. Rovers are furnishing proof that ancient Mars was wet.

Questions & Answers

Will you able to discuss what is in the astronomy as a whole?
Joecy Reply
from the beginning of astronomy 'til the present.
Joecy
till the fate of the universe
Kevin
till the universe expanding
Mr
please discuss it to me because it's hard for me to get reliable discussion of it
Joecy
hello joecy well Astronomy is not small to discuss? what do you want To discuss?
Mr
How can we differentiate between space itself expanding and the stuff within space expanding?
Jake Reply
Hello JAKE Astronomers predict that Dark energy is the reason of expansion.Think of the universe as a giant balloon. If you mark multiple points on the balloon, then blow it up, you would note that each point is moving away from all of the others. Universe is expanding from everywhere
Mr
Why does a Neutron star know as the strongest magnet in the universe instead of a Black hole?
Mr Reply
that would be a magnetar- a type of neutron star just like pulsars but with very high B fields.
Kevin
what is the cause of blackhole
DazedHotdog Reply
a collapsed massive star
donot
A dead star with intense gravity
Saaketh
star collapse remnant greater than 1.4 solar masses
Kevin
The Chandrasekhar Limit = 1.4 Solar Masses.....
Adam
when a massive star collides Under it's own weight
Mr
what is the difference between An Astronomer and a Cosmologist?
Mr Reply
cosmologist only learn cosmology right. an astronomer is learn all about astronomy, including cosmology
donot
Cosmology Is The Study Of The Universe As A Whole, Origin And Development Of The Universe.....
Adam
astronomy include cosmology, astrophysics, astrodynamic and astrometry
donot
what is astronomy
Joecy Reply
A Branch Of Science That Deals With Celestial Objects And Space.....
Adam
Is the space you had mention is about the outer space?
Joecy
Yes Outer Space.....
Adam
astronomy is the study of the universe beyond the borders of the planet.
rizza
what object can protect my pyramid being affected through doorways and interaction with others?
Christian Reply
what is big bang
Nitesh Reply
This is the blast of extremely huge sphere contains some unique particles from which our lovely universe begins
Aditya
The post-Big Bang universe was composed predominantly of hydrogen, with a little bit of helium thrown in for good measure. Gravity caused the hydrogen to collapse inward, forming structures. However, astronomers are uncertain whether the first massive blobs formed individual stars that later fell to
Mr
The Theory Of The Origin Of Our Universe.....
Adam
Adam ?
Mr
Yes Sir?
Adam
hey Adam You are right
Mr
I Hope So, Lol.....
Adam
Adam ooo well where you from?
Mr
New York City.....
Adam
And Yourself?
Adam
I am from india.I am 15 years old. you?
Mr
I Am 43 Years Old..... From New York City.....
Adam
Can you suggest me some tips to become an Astronomer ? Please
Mr
Start Learning A Lot Of Math Algebra, Calculus Trigonometry, Geometry And Scientific Notation, Get Really Good At It, Once You Can Do All That Math Proficiently, Becoming An Astronmer A Lot Easier..... And When You Win The Nobel In Astronomy, I Can Say I Know You, Lol.....
Adam
you inspired me a lot god bless you! 😄 what is your profession?
Mr
I am Vanessa Harp Future universal traveler 🌌🌌🌌
Vanessa
Iam A Doorman By Trade, I Also Have A Degree In Philosophy.....
Adam
well that's awesome dude
Mr
vanessa i am a mere amateur astronomer but if you do start traveling the universe can i tag along?
josh
I Also Am An Amateur Astronomer.....
Adam
Can we say that there is constant gravitational force in outer space instance of 0 gravity
Aditya Reply
i think garvity is not constat in every place in space,depends on the cosmic that u r near for...
Israel
I think I am right if we imagine a universe in a completely circular sphere or as an atom of some unknown element ... ....
Aditya
if you think this then think about them who use material made up of that
Ashish
element
Ashish
This is not so interesting
Aditya
I also think our universe as complex as our brain and as a computer program
Aditya
yes bro we have not that powers or that is a different dimension which a human brain does not think yet but may be possible after some time
Ashish
a group of seven stars is called
raju Reply
saptarishi
Suresh
The Pleiades.....
Adam
Why our earth or other celestial bodies is approx or completely spherically bounded why this is not square ,rectangle..... .I want to know that universal force which bound them
Aditya Reply
The most stable 3 dimensional shape which keeps the spinning material of that celestial body together in an equilibrium is a sphere. So the shapes are spheres and not squares or something different.
Ujwala
gravity. this force favors spheres and spheroids because spheres allow gravity to act equally in all directions whereas a rectangle or square wouldn't.
Mark
what do you mean by flint glass?
Suresh
which glass is called flint glass?
Suresh
who said Flint glass?
Mark
Stars, planets and moons can be made of gas, ice or rock. Get enough mass in one area, and it’s going to pull all that stuff into a roughly spherical shape. Less massive objects, such as asteroids, comets, and smaller moons have less gravity, so they may not pull into perfect spheres.
Kevin
the mass needed goes by a funny name: the potato radius
Mark
where you heared
Ashish Reply
what?
Grisha
i mean when u enter to a black hole it will take u a billions of light-years away...
Israel
yes because time slows down in more gravity
Ashish
and they said they are not always black
Israel
i don't understand this
Ashish
what do wanna say
Ashish
are black holes always black? what if there is a black hole with a blue color...
Israel
I guess black hole is called black hole because it was sucking matters that around them, including dark matter.
donot
what do u mean by "dark matter"
Israel
How man.. We don't even know what's inside the Black hole.. Just know that even light can't overcome against the gravity of BH.. So BH don't reflect any type of light..
Pavan
in universe black is not colour like other colours you can't change colour of universe because it is its nature given colour if light reflects and then come to our eyes then we saw the colour but a black hole absorbs light and never reflects it back
Ashish
are you never heard of it? well, when you look at space it never illuminated by star's lights right. space itself always look black or you can say dark although there more than zillion stars around
donot
ok then what happens to the materials which are trapped in BH when it dies
Israel
that is why scientist named them by dark matter
donot
Just quit knows about the event horizon,,,.. We don't know that what's beyond the Singularity of BH.. If any others BH singularity joins other singularity then possible well.. Don't know
Pavan
oky thanks guys...
Israel
what begin the black hole? or what is the original form of black hole? its a exploded star and black hole is just making a new star by collecting matters around them If they die, well they just became a material
donot
in our universe real and natural colour is black and light is a form of energy which emit photons colour is of that objects which are in 3 dimensions and when light reflects from these objects it comes back to our eyes space is not 3d so it is not our dimension
Ashish
Its just my thought, okay. if you wanted to know more ask some professor or search it or read a book about BH
donot
i cant know more about it becaus i had just passed my 12th class
Ashish
Well even scientists are still researching about universe we cannot sure yet, if we don't prove it
donot
its my own thinking i can't prove this now but may be in future
Ashish
really, you want to prove it too
donot
yes i wamt but at present i am a student and i have no contact to reserchers if you are then plz help me
Ashish
am also a student in 11th grade...do u some advice for me...
Israel
from which country you are
Ashish
How much u got in 12?
Pavan
from Ethiopia
Israel
i got 80 percent
Ashish
i am from india so i cant know about your country
Ashish
astronomy is world wide..ok which subjects should i pay more attention?
Israel
physics >maths >chemistry
Ashish
ok then thanks again.. stay safe..
Israel
which acid is also called chamber acid?
Suresh
sulfuric because a lead chamber was used to manufacture and process it.
Mark
thank u very much.
Suresh
i heard that black holes are not always black and they can take u to another coordinate...is this true?
Israel Reply
They have no color, and no
Cyclone
black holes have no hair.
hair?... what do you mean by that..
Israel
***en.wikipedia.org/wiki/No-hair_theorem
Black holes size gets increase by Eating massive stars and black hole are made from high massive stars who were exploded in supernova.when a black hole ears a star A quasar is formed thus a black hole is not always black
Mr
Black holes can change its shape by attracting all planets and even light
Saaketh
what is hisboson particle
Aditya Reply
Higgs Boson Is An Elementary Particle In The Standard Model Of Particle Physics, Permeates The Higgs Field Which Gives All Particles Thier Mass.....
Adam
Simply.. A god particle..
Pavan
The God Particle Is A Little Miss Leading.....
Adam
what you mean by a god particle?
vasu
God Particle Was A Nick Name They Gave It When They Had No Clue What It Was Or Did.....
Adam
so they know what it is now?
James
A field call higgs field is one of the field which are present in vacuum, just like electric, quark and gravitational fields.. So basically befor interaction of photos to this field, all are mass less.. But after interaction, electrons get some mass.. Just like a quack.. But there is very less
Pavan
Yes, It Has Been Confirmed By All The Physicists And Engineers At Cern, Large Haldron Collider.....
Adam
Interaction between field and hisboson.. So they remain mass less..
Pavan
Simply call.. God Particles.. 😊
Pavan
why space is black?
Akash Reply
Hubble's Law, the Doppler Effect, and the lack of objects to reflect light
Cody
read on Olber's paradox
Kevin
because it night there man
Grisha
Olber's Paradox.....
Adam
Dark matter!
Pavan
what is the best book in order to study astronomy.
jawad
personally i don't use a book, but any book is good
daniel
I know it sounds funny but I picked up a few books including Astronomy For Dummies. I also got a couple from Neil Tyson, he has some simple into books.
josh
tell me any lectures that are available on YouTube for astronomy as a beginner.
jawad
Crash course- Astrophysics. that's the beginner course on YouTube.
Kevin
And anything from the brilliant Director of the Hayden Planetarium, Neil deGrasse Tyson
Bill
there is alit on you tube luke bill said NGT has alot of into stuff. Brian Green is good at makin tv thing simple and when your ready Lawernece Krauss is good too.
josh
Amy Mainzer is especially good.
Because Space is Not a Object light can't reflected but it.light simply passes thoughtout the space and about 90%of the space is Dark because their is No star or quasar to Emit light
Mr
could get a suggestion to become a good astronomer
Monisha
monisha sure
Mr
Well You should be curious about space and Astronomy and then you would must become a good Astronomer
Mr
oh thank you
Monisha
you are very welcome
Mr
can i know which course i'll choose to study in higher studies
Monisha
well it requires pHd in the field of Astronomy which would take 5-6 years to complete it
Mr

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Source:  OpenStax, Astronomy. OpenStax CNX. Apr 12, 2017 Download for free at http://cnx.org/content/col11992/1.13
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