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In places like southern Canada, a glowing, purple ribbon of light sometimes crosses the sky.
It’s pretty faint, and it sometimes has these green spikes called the picket fence.
It’s also pretty speedy, moving steadily east to west about six-and-a-half kilometers per second.
Citizen scientists and photographers have known about it for a long time,
because it keeps photobombing their pictures of auroras.
And after years of seeing it, they even gave it a name: Steve, after the scene from the movie Over the Hedge.
But they just assumed it was a funny kind of aurora, or at least something similar.
Then, in 2016, Steve caught the attention of professional scientists,
who realized this streak might be something new.
And last Monday, one team published a paper in Geophysical Research Letters with the newest explanation for it.
According to their results, Steve… is like nothing we’ve ever seen before.
It might be a whole new kind of northern light.
Even though citizens scientists kind of named this streak as a joke, scientists decided to roll with it,
and they formally called this light the Strong Thermal Emission Velocity Enhancement.
Which is pretty amazing.
They could immediately tell it was different from normal auroras for a few reasons.
First, auroras usually only appear at lower latitudes during periods of especially high solar activity,
but STEVE is a consistently lower-latitude event.
And its shape and speed don’t really match other auroras, which tend to be broader, undulating structures.
Plus, auroras tend to be green or red; purple usually only shows up in extreme cases.
Because of this, scientists wondered if there was a unique mechanism at play.
Earlier this year, one team published the first explanation for STEVE.
They suggested it might be caused by something called a subauroral ion drift, or SAID.
SAIDs aren’t auroras: Instead, they’re fast, westward flows of charged gas associated with solar storms.
That sounds a lot like our purple streak, but STEVE doesn’t only appear during solar storms,
and it moves much faster than SAIDs typically do.
SAIDs also rarely produce visible light emissions.
So in last week’s paper, another team took a different approach to the mystery.
Since the SAID hypothesis already had some holes in it,
the group wanted to see if STEVE could be formally considered an aurora, even if it was an unusual one.
Auroras happen when energetic electrons and protons from the Sun precipitate through the Earth’s atmosphere,
exciting those gases and making them glow.
So if STEVE is an auroral event, then scientists should be able to detect these particles when the streak appears.
The paper’s authors used ground-based and satellite data taken during one of STEVE’s 2008 appearances to try and hunt them down.
Except, there wasn’t much, at least, in the way of energetic particles.
So that rules out STEVE as an aurora.
That means, at least right now, this purple light is in a class all its own.
It’s just… a STEVE, probably driven by its own special mechanism.
But that doesn’t mean we’ll stop investigating it.
The next steps are to study more STEVE events,
since scientists have only really looked at two of them so far.
And ideally, that will help us not just understand this light,
but how the Sun creates different kinds of auroras in general.
While those scientists keep working on that mystery, another team is celebrating a new discovery.
According to a paper published in PNAS last Monday,
researchers have found direct evidence of water ice on the surface of the Moon!
And that could be big news for future explorers.
The new discovery was made thanks to Chandrayaan-1,
a lunar orbiter launched in 2008 by the Indian Space Research Organization.
Its payloads mostly focused on mapping and studying the Moon’s composition,
and it did some really cool science for almost a year before a communication failure ended the mission.
The data for this new paper specifically came from the orbiter’s M3 instrument,
or the Moon Mineralogy Mapper, which was built by NASA’s Jet Propulsion Laboratory.
It’s a type of spectrometer,
which means it measured the wavelengths of light that reflected off the Moon’s surface
and used them to determine composition.
About ten years ago, back when Chandrayaan-1 was still active,
M3 found some evidence for water ice on the surface, which was really exciting.
But the evidence was pretty indirect, and it wasn’t obvious just how much ice there was.
Plus, that data included water that was part of hydrated minerals,
so it wasn’t pure ice or anything.
But now, things seem different.
This newly-analyzed data directly confirmed the presence of that ice,
and it also suggests that at least some of it could be pure water,
although more observations would help pin that down.
These ice deposits are scattered around the Moon’s north and south poles,
and a lot of it is in shadowy southern craters.
There, it never sees the light of day, thanks to how the Moon is tilted relative to the Sun.
That keeps the ice from melting and makes the deposits relatively nice and accessible.
So far, we don’t really know how all that ice got there or how old it is.
But this icy discovery is really promising for future missions.
As of right now, NASA is planning to send people back to the Moon,
so this ice could potentially become a source of drinking water.
But maybe more importantly, if we can split it into hydrogen and oxygen on a large scale,
it could also be used for rocket fuel.
The Moon could be an interplanetary gas station! Well, someday.
There’s still a long way to go, but thankfully, that ice doesn’t seem to be going anywhere.
Thanks for watching this episode of SciShow Space News!
And thanks especially to our Patrons who make it possible for us to research new science and create this videos for you.
Thank you!
And if your name is Steve or Chandrayaan, let us know in the comments, because awesome.
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