Mercury · Solaris Wiki | World Anvil


Welcome to Solaris, traveller! This is a slower-than-light science fantasy set in our own solar system.
About Solaris | Guide to Solaris | Prologue
Content Warning:
This article discusses imperialism and colonialism in the section called "Lost Grandeur". Mercury has been invaded twice by the sun, which has caused the ecological collapse of the planet. This article references the outcomes of this.
Mercury was once the economic center of the Sol System, but today most of its people are refugees. The Scorching of Mercury has left the planet an arid husk of its former glory. A small amount of factories and mines are still operational, buried deep enough into the crust of Mercury to avoid the extreme outside temperatures. The workers of these factories spend their entire life underground now that the surface has become so hostile.   The defense of Mercury is orchestrated by the Interplanetary Solar Defence Council, which is headed from the satelite station Caduceus with a surface-side presence in the migratory military base Penumbra. A small group of civilians tail Penumbra, either to support or to seek shelter with them.  

Solar Cycle

The sun has always had a profound impact on Mercury, in no small part due to the resonances of its orbit. The planet spins around itself one and a half times faster than it orbits the sun. Not only does this make the sun appear to move backwards through to the sky, it makes a Mercurian day last twice as long as a Mercurian year.   It takes 176 days for Mercury to complete one solar cycle, so each phase of the day is roughly analogous to a season. The transitional dawn and dusk phases last around 12 days, while the diurnal and nocturnal phases last for an average of 76 days.   Even before the Scorching of Mercury, Mercury's seasons would lead to extreme peaks of heat and cold. With the loss of atmosphere the differences have risen to extremes. The diurnal phase gets hot enough to boil off any liquids on the surface, an almost intolerable heat. Meanwhile the night, without any atmosphere to retain the heat and keep it from simply radiating back out into space, the nocturnal phase gets far below freezing.  

Phases of the Solar Cycle

Dawn Phase12 days
Diurnal Phase76 days
Dusk Phase12 days
Nocturnal Phase76 days

For a more indepth visualization see: A Day in the Caloris Basin

A vintage travel poster for Mercury. It says
Visit Mercury by Annie Stein

Planet of the Still Sun

The traditional Mercurian calendar begins when the Sun stops over Hun Kal at the perihelion of Mercury's orbit. This event, known as the Still Sun, occurs when the sun stops in the sky, then reverses and moves forward for a few days, before ultimately stopping again and resuming it's backwards motion.   Mercury's tourism boomed as the planet neared perihelion. Many came to partake in the festivities and observe the phenomena, sometimes even returning to get another perspective. At Hun Kal, the sun reverses during high noon of the Still Sun. Cities along the western edge of the terminator experienced a double dawn, while the eastern edge observed a double dusk.   This oddity of Mercury's solar cycle occurs because the speed of Mercury's orbit is not consistent. When the orbit is at perihelion, the closest to the Sun itself, the orbital speed picks up enough that the sun is finally moving faster through the sky than Mercury is spinning on it's own axis.

Terminator Migration

  Those who live on the surface of Mercury after the Scorching survive by migrating along the terminator. The slow solar cycle and the small size of the planet makes it viable to travel to always remain in the twilight. The terminator slowly circles the planet at at around 3.6 km/h or 2.2 mph.   Most nomads, and the migratory military base Penumbra, travel to the edge of dusk, and stay there until dawn. This usually allows them to stay still for about a week before they resume moving. Others chose to constantly travel, only pausing to sleep and then get moving again.
Settlement | Nov 10, 2023

In the shadows of the Iron Spires, migrating along the terminator, walks Penumbra. Soldiers, mercenaries, and civilians alike warily watch the sky, always prepared for another Solar Pulse.


Lost Grandeur

  The Mercurians were not the earliest spacefarers, but they took to it like no others. They rapidly expanded across the Sol System, led by explorers and followed by merchants. At the largest, their merchant empire stretched all the way from Mercury, out to Pluto in the Kuiper Belt. What started as trading outposts eventually became colonies as the Mercurian Imperial project began in the Late Spacefaring era. Mercurian nations sprung up on moons and planets across the Solar system.   Resources, and thus wealth, flowed out from the planets and colonies they were extracted from back to the imperial core. Although some of the surplus of this rich trade was captured by enterpreneurial Mercurians who established plantations and companies abroad, the majority of the wealth was concentrated among a small elite. The colonizers were loathe to give up any of the creature comforts of their home, though, and Mercury became associated with opulence as luxury goods found their way first to the colonies, then to the colonized populace.   Towards the end of the Imperial period, the complexity of the colonial networks reached a zenith. Each colony functioned as a node in a larger web of goods, and some products passed through multiple colonies before reaching Mercury. The revolts that ended the period were thus accompanied by an extended period of economic upheaval as colony after colony crashed out of this web, and some products were never produced again, while others eventually returned as a result of more equitable trade.   The colonial revolts are not forgotten. Efforts towards reparations were started not long after the end of the empire, but the hardships the Mercurian people have suffered since the start of the Scorching caused many of these programs to be halted or cancelled entirely. Some criticize the fact that Mercurian elite, the chief benefactors of the Sol-wide system of exploitation, still maintain a substantial amount of their wealth in the form of off-Mercury assets and investments. These voices are increasingly quiet, however, as public sympathy towards Mercury mounts.

See Also

Planets Mercury · Venus · Tellus · Mars · Jupiter · Saturn · Uranus · Neptune
History Scorching of Mercury
Locations Caduceus · Penumbra · Biomes ( Sunbleached Wastelands ) · Iron Spires ( Hokusai · Hun Kal )
Characters Blue NM-2 · Eun · Sciah · Roseah · Tray
Species Keras ( Mot · Walker )
Politics Ruling ( Mercurian Triumvirate · Interplanetary Solar Defence Council ) · Keystone of Mercury
Society Ethnicities ( Refugees of Mercury · Nomads of Mercury ) · Borealis Ice Mining
88 days
Solar Cycle
176 Days
Natural Satellites
Artificial Satellites
Location under
Owning Organization
Inhabiting Species
Table of Contents
Notice: This article is a stub. If you'd like to see this article expanded, please leave a comment!

1st Solar Invasion

220010 220014

Also known as the Scorching of Mercury, the first Solar Invasion of Mercury began in the year of 220010. Despite interplanetary intervention in the form of the Interplanetary Solar Defense Council, Mercury fell to the onslaught and ecological collapse.

Read more about the Scorching of Mercury

  • 220010


    Diplomatic action

    Debates on whether to respond by war or disaster protocols delay action from the Alliance of Nations.

  • 220010

    1 /1

    Destruction of Hun Kal
    Disaster / Destruction

    Hun Kal was the first city to fall. A team was sent out to explore; they found a destroyed atmodome, a melted city, and millions of desperate people caught in the rubble.

    Hun Kal
  • 220011


    Interplanetary Solar Defense Council

    Established by the Alliance of Nations to coordinate the defense of Mercury. Some of the terms of the demilitarization contract were waived to allow the ISDC's creation.

    Additional timelines
  • 220011


    Ecological Collapse of Mercury
    Disaster / Destruction

    Not only was Mercury invaded, the increased solar activity and the presence of the Scourge eroded the atmosphere of Mercury.

  • 220014

    100 Day Vigil

    The faithful of the Keystone of Mercury gather in prayer.


Please Login in order to comment!
Nov 11, 2023 18:10 by Mochi

The time it took to make this article really paid off! Loved it <3

I hope you have a great day!   Explore the endless planets brimming with life of the Yonderverse! Go after creatures, discover new places, and learn about the people you find along the way.   Check out my new world, Ava Admira!
Nov 11, 2023 18:21 by Annie Stein

Thank you so much!

Creator of Solaris -— Come Explore!
Nov 11, 2023 18:19 by Emily Armstrong

Really fantastic article, totally going into my inspo for planet articles! And loove the travel poster, so fun!! Great job!

Check out my worlds of Beckettville and Culinarypunk!
Nov 11, 2023 18:22 by Annie Stein

Ah, thank you! It was a last minute bout of inspiration, I'm very happy with how the poster turned out!

Creator of Solaris -— Come Explore!
Nov 11, 2023 22:11 by Chris L

Beautifully done Annie! Really lovely work as always and as always I appreciate the thought and care you put into your articles.

See WorldEmber 2023 Hub for my WorldEmber progress.

Check out my challenge winning article: Ghost Boy.

Nov 11, 2023 22:11 by Annie Stein

Thank you so much!

Creator of Solaris -— Come Explore!
Nov 12, 2023 21:22 by Aster Blackwell

The section on the Imperial period is fascinating! I love how complicated the political scene of Solaris is, it really makes it feel like a real place.

Nov 12, 2023 21:34 by Annie Stein

Thank you! I'm very glad to hear that!

Creator of Solaris -— Come Explore!
Nov 13, 2023 16:54 by Dr Emily Vair-Turnbull

Really interesting article. I particularly love the travel poster.   Poor Mercury. :(

Emy x   Etrea | Vazdimet
Nov 13, 2023 19:53 by Annie Stein

Thank you, it was fun to draw! And yes, gosh, poor mercury.

Creator of Solaris -— Come Explore!
Nov 25, 2023 12:56 by Rin Garnett

I would 100% visit to see the Still Sun. If, you know, there was still an atmosphere and stuff. Darn Scorching, ruining perfectly good tourist destinations...

Nov 25, 2023 15:16 by Annie Stein

The true tragedy!

Creator of Solaris -— Come Explore!
Dec 18, 2023 15:04 by Reanna R

Wow, it seems like it would be such a cool place to visit, with all those interesting astronomical events! If, you know, it weren't for the scorching, and the fact that it's mostly inhabited by nomads...

May your worldbuilding hammer always fall true! Also, check out the world of the Skydwellers for lots of aerial adventures.
Dec 18, 2023 15:22 by Annie Stein

Should've gone before the scorching! Y'can't trust a planet to be there next year.

Creator of Solaris -— Come Explore!
Jan 24, 2024 19:11 by Amélie I. S. Debruyne

Oooooh! This is a fascinating past for Mercury! This really got to make the current situation very complex for all Mercuriens refugees... On the other hand, it also gives them contact through the empire and the resources to move the population of almost an entire planet!

To see what I am up to: World Ember 2023 list of articles.
Jan 25, 2024 11:49 by Annie Stein

Yes, exactly!

Creator of Solaris -— Come Explore!