[X] My Assistant

[jasedm]

As of today, we have photographs and maps of many of the surfaces of the larger solid bodies of the solar system (including two shrouded in dense atmospheres) I was wondering what are the largest expanses of unknown terrain (by this I mean not imaged at a resolution better than 15km or so) remaining in the solar system today, and came up with the following.

The figures are inevitably approximate, are in square kilometres and I'm ignoring our own planet's ocean-floors.

Mercury (the 30-ish% not photographed by Mariner or radar-imaged from Arecibo) - 22,500,000
Pluto/Charon - 21,310,000
Titan (the remaining 25-ish% not yet imaged from Cassini) - 20,825,000
Eris - (dwarf planet/TNO) - 18,100,000
Neptune system (~half of Triton plus Proteus and Nereid) - 13,600,000
Uranus system (Over half of each of the moons Miranda through Oberon) - 13,400,000
Jupiter system (pole areas of the galileans) 11,600,000
2005fy9 - (TNO) - 10,200,000
2003el61 - (TNO) - 6,970,000
Sedna - (TNO) - 6,970,000
Quaoar - (TNO) - 4,990,000
Ceres/Vesta - 3,722,000 (I've lumped these together for obvious reasons)

For comparison, these add up to just over the dry-land surface of Earth (which is 148,940,000 square km)

Incidentally, pre-Cassini, Titan alone comes out at 83,300,000 square km

Interesting to note that the top three will have been imaged at good or very good resolution in the next ten to fifteen years.
We may get a mission each to Uranus and Neptune in my lifetime, but I don't expect my children will get to see what Eris looks like up-close in theirs.

[jasedm]

True, and everything is fascinating. From the fluffball that is Methone, to the amazing landscapes on Churyumov-Gerasimenko, to Pluto/Charon (who envisaged they would be so dynamic prior to New Horizons?)

I think Psyche will be quite something to see up-close, and I'm really looking forward to Europa Clipper

[JRehling]

FWIW, Pallas has about 800K km^2 of area, but the resolution for asteroids observed from Earth is already approaching, and will likely within the next decade exceed the offered threshold.

For many worlds (e.g., Pluto, Charon, and the satellites of Uranus and Neptune) the unobserved territory is going to be largely or entirely represented by the territory already observed. To some extent, lower resolution imagery can corroborate that likelihood. So in that respect, I'd say that Eris looms as plausibly the main repository of truly unknown terrain. The fact that Triton and Pluto turned out to be as different as they are bolsters the curiosity, I'd say, about how Eris evolved.

Of course, we never know what we don't know, and some small world or some highly anomalous tidbit of a world we've already seen in part may turn out to be startlingly unique. Maybe the 5th or 10th biggest KBO will turn out to be the most interesting one.