Over the past 50 years or so, we’ve gotten pretty good at exploring our solar system.
And one day, maybe our spacecraft will regularly venture beyond that — into interstellar space.
Still, there are a lot of challenges we’ll need to tackle to achieve that goal, including navigation.
After all, space is big, and it’s not like there’s a galactic version of GPS.
But this month, researchers announced developments on a promising way
we could someday steer spacecraft on deep space missions: using pulsars.
Pulsars are the leftover, super-dense cores of massive stars that went supernova.
They spin super fast — as often as thousands of rotations every second
and their incredibly strong magnetic fields accelerate particles away from them in jets.
Those jets emit a lot of radiation.
In a way, they’re kind of cosmic lighthouses.
If a pulsar is oriented correctly with respect to Earth,
its rotating jets will sweep across our line of sight and make its signal appear to pulse.
Because those pulses are so regularly-timed,
we’ve thought for decades that pulsars could be used like beacons.
In theory, a spacecraft could determine its position by tracking the signals
it receives from multiple pulsars.
It was such a promising idea that, in the 1970s, a map of how to find our solar system
relative to 14 different pulsars was included on the Pioneer and Voyager spacecraft.
Although, back then, it was only a theoretical tool.
Our technology just wasn’t ready for the job.
But this month, at an American Astronomical Society meeting,
NASA researchers announced that pulsar navigation is one step closer to reality.
Last November, they tested this method using the SEXTANT enhancement
on a washing machine-sized instrument on the International Space Station.
With it, the team was able to pinpoint the Station’s position
to within about 5 kilometers using the x-ray emissions from just four pulsars.
That’s pretty impressive, considering the ISS is flying around the Earth
at around 28 thousand kilometers per hour.
Pulsars are found all over galaxy,
so one of the perks of navigating by them is they can be used anywhere in space.
But perhaps the most important perk is autonomy.
Pulsars remove the need for spacecraft to regularly communicate with Earth to steer.
Instead of waiting for commands from Earth,
pulsar navigation would allow a spacecraft to make small decisions by itself.
It would also allow a craft to change trajectory during times when it can’t connect with Earth
like if the Sun is in the way.
So far, this research is just proof of concept,
and it could take years to implement a galactic positioning system in real spacecraft.
But a second SEXTANT experiment is set for later this year,
and astronomers are working both on improving the algorithms behind it
as well as designing a smaller, more lightweight instrument.
Because in space, size matters!
And something the size of a washing machine just won’t do.
We might still be figuring out how to navigate interstellar space,
but there is a place in the solar system with a brand new map:
Titan, Saturn’s largest moon.
Last month in Geophysical Review Letters,
astronomers published the most advanced topographic map of Titan to date,
as well as a paper announcing new revelations — and new mysteries.
Scientists are especially interested in Titan because it’s a bit of an oddball.
For one, it has a super thick, nitrogen-rich atmosphere,
while most moons don’t have much of an atmosphere at all.
It’s also the only object besides Earth where we’ve definitely found liquid on its surface
although it’s not water.
It’s simple organic molecules like methane and ethane,
which are made of carbon and hydrogen.
This new map combines all the data from the Cassini mission to Saturn,
which ended last year, but computer algorithms had to help fill in the gaps.
It probably won’t explain Titan’s weird atmosphere or anything,
but the map is already helping astronomers better understand the moon’s surface features.
The map showed new mountains, helped refined measurements of Titan’s shape,
and revealed that Titan’s three hydrocarbon seas all sit at the same elevation.
In other words, they form a single sea level, just like Earth’s oceans do.
Mostly, this is cool because it means Cassini took really accurate data.
Like, it could measure altitude with accuracy down to 40 centimeters!
The map also proved that some of Titan’s lakes — which are isolated from its seas
are connected with each other underneath the surface.
They noticed this because, for groups of lakes that share the same drainage basin,
all of the dry lake beds sit at higher elevations than nearby filled lakes.
But there weren’t any visible rivers flowing from one lake to another.
That means the liquid likely used underground channels
to drain into the lakes closer to sea level.
Maybe the weirdest new discovery about the moon were depressions
that look a bit like someone took a cookie cutter to Titan’s surface.
They’re flat-floored lake basins surrounded by ridges hundreds of meters high!
They appear to have formed the same way certain terrain, called karst, does on Earth:
when underground material is dissolved by running liquid,
then the surface material collapses to form a giant hole.
But on Titan, the rims of these depressions are sharper, and the walls are steeper.
Right now, it’s still a big mystery how these features formed and evolved
and if they mean anything for Titan as a whole
but we probably won’t have an answer any time soon.
We’ll have to wait until Titan gets another satellite visitor to get more high-resolution
data.
But in the meantime, we can at least continue to dig through
what Cassini provided over its 13 years zooming around Saturn.
And this new map is only the beginning.
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