newbie question about 'Goldilocks Zones'

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good morning ladies and gents -

newbie here who was wondering about 'Goldilocks' zones in the solar system..

As I understand it, the following places are considered to be warm enough and safe enough for live - Planet Earth, Mars, underneath the Europan Ice crust, possible warm oceans on Neptune/Uranus.

I was wondering, if it had been considered that on Mercury, there must be places where the temperature is just about right. On the side that faces the sun, its understood that temperatures can reach 400C and on the side facing away -180C.. does this not mean that surely there is a point inbetween the two where temps would range between 0 and 30C?.. possibly having to follow it around the planet as it rotates?? I assume it would be an area not facing direct sunlight, so relatively safe from solar radiation.

would welcome any thoughts/corrections - thanks


Mercury is a bad choice for life due to the lack of water and atmosphere. But I think that is good question to wonder if life could exist on a tidally locked planet in the 'twilight zone'. It certainly doesn't sound like an ideal condition for the formation of life, but it may be possible.


Mercury is not tidally locked.

For every two orbits around the Sun, Mercury rotates three times.

Mercury takes 88 days to orbit the Sun, but rotates once every 59 days, so each time Mercury orbits the Sun, the opposite side of Mercury is facing the Sun.

The mythical 'Twilight Zone' of Mercury does not exist as was once thought if Mercury was Heliosynchronous.

At Dawn on the Equator on Mercury, the ground temperature is approx minus 186 Celsius. At Noon it has climbed to 407 Celsius (hot enough to melt lead). Early afternoon reaches 427 Celsius. Sunset it has fallen to minus 23 C. Midnight, minus 170 Celsius. Dawn minus 186 Celsius again.

On the floors of the permanently shadowed polar craters on Mercury, temperatures may be below minus 250 Celsius!!!!!

Just to say the supposed ocean under the ice crust of Europa is theoretical, there is as yet no direct 100% proof of it's existence.

The Goldilocks Zone assumes an Earth clone. Venus & Mars are both just about within the Sun's Goldilocks Zone, but both are very hostile. The Moon orbits the Earth!!!!!

As mentioned objects further out like tidally heated moons, Jupiter's Io being an extreme example, Saturn's Enceladus being a lesser example or deep oceans that may exists inside Uranus & Neptune may be potential abodes, assuming the correct chemistry can occur.

Andrew Brown.


Interesting stuff, It must then be theoretically possible that a region of the Moon has a 'goldilocks' zone, but I've never heard anything about it. With all the new discoveries over the last 40 years or so, It seems the days of requiring an Earth like planet for life are long gone.

Mercury is obviously a bad place for life, I recently saw an ABC documentary on the planets and it refered to Enceladus as being a possibility, and already proof is there that it has an ocean within its surface. If we were to make a list of possible places for life in our solar system, and rank it according to probability of life being found/having developed I would assume it would look something like this:

Direct Evidence of Life:
1 Earth (abundant life)

Possibility of Life based on Earth-like temperatures and protection from solar radiation

2 Enceladus:
Positives + Evidence of warm ocean and complex carbon based molecules found and observed
Negatives - None I know of

3 Mars:
+ Temperatures just within Earth-like range, Evidence of water found, Thin atmosphere to protect from Solar Radiation, unusual proportions of life bearing chemicals found within underground cave networks)
- None found so far on inspections. No magnetic field to protect the thin atmosphere. Slightly too cold in most parts of the planet to sustain Earth-like life; No oxygen

4 Europa:
+ Specualation of warm earth like oceans and protected from the sun by a permanent ice crust
- no direct evidence of the existence of any oceans;

5 Neptune:
+ Speculation of warm earth like oceans and protected from the sun by thick dense atmosphere. Evidence of water because of blue colouring. Evidence of a warm core to heat the ocean.
- Not enough known about the interior of the ice giant planets, so everything remains pure guess work

6 Uranus:
+ similar to Neptune,
- not as likely as Neptune to contain solely water based oceans; Strange seasons due to 90degree axial tilt may affect temperatures within the oceans?

Life Unknown and Based on different properties;

7 Titan:
+ direct evidence of complex carbon based molecules and thick dense atmosphere to protect from solar radiation
- extremely cold temperatures; no oxygen; no directly observed life on landing of Huygens probe

Other Possiblities:

8 Life within the clouds of Venus/Jupiter/Saturn
9 Other 'goldilocks' zones within the solar system, The Moon and Mercury, as discussed in the OP.
10 Unexplored worlds may yet shock us, Pluto (2015) and Kuiper belt objects
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