Enceladus’ Jets Selectively Power-Up Farther From Saturn

Icy water vapor geysers erupting from fissures on Enceladus. Credit: NASA/JPL

A crowning achievement of the Cassini mission to Saturn is the discovery of water vapor jets spraying out from Enceladus‘ southern pole. First witnessed by the spacecraft in 2005, these icy geysers propelled the little 515-kilometer-wide moon into the scientific spotlight and literally rewrote the mission’s objectives. After 22 flybys of Enceladus during its nearly twelve years in orbit around Saturn, Cassini has gathered enough data to determine that there is a global subsurface ocean of salty liquid water beneath Enceladus’ frozen crust—an ocean that gets sprayed into space from long “tiger stripe” fissures running across the moon’s southern pole.  Now, new research has shown that at least some of the vapor jets get a boost in activity when Enceladus is farther from Saturn.

The gravitational pull of Saturn changes the amount of particles spraying from Enceladus at different points in its orbit. When it's farther from Saturn (left) the plume contains more icy particles and thus appears brighter. Credit: NASA/JPL-Caltech/University of Arizona/Cornell/SSI.
The gravitational pull of Saturn changes the amount of particles spraying from Enceladus at different points in its orbit. When it’s farther from Saturn (left) the plume contains more icy particles and thus appears brighter. Credit: NASA/JPL-Caltech/University of Arizona/Cornell/SSI.

By measuring the changes in brightness of a distant background star as Enceladus’ plumes passed in front of it in March 2016, Cassini observed a significant increase in the amount of icy particles being ejected by one particular jet source.

"Baghdad Sulcus," one of Enceladus' plume sources, imaged by Cassini during a close pass in Nov. 2011. (NASA/JPL/SSI)
“Baghdad Sulcus,” one of Enceladus’ plume sources, imaged by Cassini during a close pass in Nov. 2011. (NASA/JPL/SSI)

Named “Baghdad 1,” the jet went from contributing 2% of the total vapor content of the entire plume area to 8% when Enceladus was at the farthest point in its slightly-eccentric orbit around Saturn. This small yet significant discovery indicates that, although Enceladus’ plumes are reacting to morphological changes to the moon’s crust due to tidal flexing, it’s select small-scale jets that are exhibiting the most variation in output (rather than a simple, general increase in outgassing across the full plumes.)

“How do the tiger stripe fissures respond to the push and pull of tidal forces as Enceladus goes around its orbit to explain this difference? We now have new clues!” said Candice Hansen, senior scientist at the Planetary Science Institute and lead planner of the study. “It may be that the individual jet sources along the tiger stripes have a particular shape or width that responds most strongly to the tidal forcing each orbit to boost more ice grains at this orbital longitude.”

The confirmation that Enceladus shows an increase in overall plume output at farther points from Saturn was first made in 2013.

Whether this new finding means that the internal structure of the fissures is different than what scientists have suspected or some other process is at work either within Enceladus or in its orbit around Saturn still remains to be determined.

“Since we can only see what’s going on above the surface, at the end of the day, it’s up to the modelers to take this data and figure out what’s going on underground,” said Hansen.

Sources: Planetary Science Institute and NASA/JPL

Enceladus' water ice plumes were first observed by Cassini in 2005. (NASA/JPL/SSI)
Enceladus’ now-famous water ice plumes were first observed by Cassini in 2005. (NASA/JPL/SSI)

Spotlight On Pluto’s Frozen Polar Canyons

This enhanced color view Long canyons run vertically across the polar area—part of the informally named Lowell Regio, named for Percival Lowell, who founded Lowell Observatory and initiated the search that led to Pluto’s discovery. The widest of the canyons is about 45 miles (75 kilometers) wide and runs close to the north pole. Roughly parallel subsidiary canyons to the east and west are approximately 6 miles (10 kilometers) wide.
This enhanced color view Long canyons run vertically across the polar area—part of the informally named Lowell Regio, named for Percival Lowell, who founded Lowell Observatory and initiated the search that led to Pluto’s discovery. The widest of the canyons is about 45 miles (75 kilometers) wide and runs close to the north pole. Roughly parallel subsidiary canyons to the east and west are approximately 6 miles (10 kilometers) wide.
This enhanced color view shows long canyons running vertically across Pluto’s north polar region — part of the informally named Lowell Regio, named for Percival Lowell, who founded Lowell Observatory and initiated the search that led to Pluto’s discovery. The widest of the canyons is about 45 miles (75 km) wide and runs close to the north pole. Roughly parallel secondary canyons to the east and west are approximately 6 miles (10 km) wide. Click for a hi-res view. Credit: NASA/JHUAPL/SRI

Pluto’s frozen nitrogen custard “heart” has certainly received its share of attention. Dozens of wide and close-up photos homing on this fascinating region rimmed by mountains and badlands have been relayed back to Earth by NASA’s New Horizons probe after last July’s flyby. For being only 1,473 miles (2,370 km) in diameter, Pluto displays an incredible diversity of landscapes.

Annotated version of Pluto's north polar region.
Annotated version showing sinuous valleys, canyons and depressions and irregular-shaped pits. Credit: NASA/JHUAPL/SRI with additional annotations by the author

This week, the New Horizons team shifted its focus northward, re-releasing an enhanced color image of the north polar area that was originally part of a high-resolution full-disk photograph of Pluto. Inside of the widest canyon, you can trace the sinuous outline of a narrower valley similar in outward appearance to the Moon’s Alpine Valleycut by a narrow, curvy rill that once served as a conduit for lava.

A composite of enhanced color images of Pluto (lower right) and Charon (upper left), taken by NASA's New Horizons spacecraft as it passed through the Pluto system on July 14, 2015. This image highlights the striking differences between Pluto and Charon. The color and brightness of both Pluto and Charon have been processed identically to allow direct comparison of their surface properties, and to highlight the similarity between Charon's polar red terrain and Pluto's equatorial red terrain. Pluto and Charon are shown with approximately correct relative sizes, but their true separation is not to scale.
A composite of enhanced color images of Pluto (lower right) and Charon, taken by NASA’s New Horizons spacecraft on July 14, 2015. This image highlights the striking differences between Pluto and Charon. The color and brightness of both Pluto and Charon have been processed identically to allow direct comparison of their surface properties, and to highlight the similarity between Charon’s polar red terrain and Pluto’s equatorial red terrain. Pluto and Charon are shown with approximately correct relative sizes, but their separation is not to scale. Credit: NASA/JHUAPL/SRI

We see multiple canyons in Pluto’s polar region, their walls broken and degraded compared to canyons seen elsewhere on the planet. Signs that they may be older and made of weaker materials and likely formed in ancient times when Pluto was more tectonically active. Perhaps they’re related to that long-ago dance between Pluto and its largest moon Charon as the two transitioned into their current tidally-locked embrace.

Cropped version showing three, odd-shaped pits that may reflect sinking of Pluto's crust. Credit:
Cropped version with arrows pointing to three, odd-shaped pits that may reflect sinking of Pluto’s crust. Credit: NASA/JHUAPL/SRI

In the lower right corner of the image, check out those funky-shaped pits that resemble the melting outlines of boot prints in the snow. They reach 45 miles (70 km) across and 2.5 miles (4 km) deep and may indicate locations where subsurface ice has melted or sublimated (vaporized) from below, causing the ground to collapse.

Notice the variation in color across the landscape from yellow-orange to pale blue. High elevations show up in a distinctive yellow, not seen elsewhere on Pluto, with lower elevations and latitudes a bluish gray. New Horizons’ infrared measurements show abundant methane ice across the Lowell Region, with relatively little nitrogen ice. The yellow terrains may be older methane deposits that have been more processed by solar UV light than the bluer terrain. The color variations are especially striking in the area of the collapse pits.

The new map shows exposed water ice to be considerably more widespread across Pluto's surface than was previously known - an important discovery.
The new map shows exposed water ice at Pluto to be considerably more widespread across its surface than was previously known. Its greatest concentration lies in the red-hued regions (in visual light) to the west of Tombaugh Regio, the large, heart-shaped feature. Credit: NASA/JHUAPL/SRI

Pluto’s icy riches include not only methane and nitrogen but also water, which forms the planet’s bedrock. NASA poetically refers to the water ice as “the canvas on which (Pluto’s) more volatile ices paint their seasonally changing patterns”. Recent images made in infrared light shows little or no water ice in the informally named places called Sputnik Planum (the left or western region of Pluto’s “heart”) and Lowell Regio. This indicates that at least in these regions, Pluto’s bedrock remains well hidden beneath a thick blanket of other ices such as methane, nitrogen and carbon monoxide.

To delve more deeply into Pluto, visit the NASA’s photojournal archive, where you’ll find 130 photos (and counting!) of the dwarf planet and its satellites.

Did We Need the Moon for Life?

Did We Need the Moon for Life?

Astronomers hate the Moon because it ruins perfectly good observing nights. But is it possible that we all need the Moon for our very existence?

For all we know, Earth is the only place in the Universe where life appeared. This makes the mystery of our existence even more puzzling. What were all the factors required to bring about the first lifeforms on our planet, and encourage the evolution of more complex, intelligent lifeforms.

We needed a calm and reasonable Sun, solid ground, nice temperatures, the appropriate chemicals, and liquid water. Possibly drinks served in pineapples with little umbrellas. But what about the Moon? Is the Moon a necessity for life in any way?

To the best of our knowledge, our Moon was formed when a Mars-sized object smashed into the Earth about 4.5 billion years ago. This enormous collision spun out a cloud of debris that coalesced into the Moon we know and love today.

Back then, the Moon was much closer to the Earth than it is today, a mere 20-30,000 kilometers. A fraction of its current distance. If you could have stood on the surface of the Earth, the Moon would have looked 10 to 20 times bigger than we see it today.

But nobody did, because the Earth was a molten ball of red hot magma, tasty lava through and through. Life emerged 3.8 billion years ago, pretty much the day after Earth had cooled down to the point that it was possible for life to form.

Scientists think that it first formed in the oceans, where there were adequate temperatures and abundant water as a solvent for life’s chemicals to mix.

The effect of gravity is a cube of its distance. When the Moon was closer, the power of its gravity to pull the Earth’s water around was more ferocious. But what impact has this gravity had on our world and its life? Do we need the Moon to make the magic happen?

Turns out, we might owe our very existence to it because its pull of gravity might have set our plate tectonics in motion. Without plate tectonics, our planet might be more like Venus, toasty and dead.

Map of the Earth showing fault lines (blue) and zones of volcanic activity (red). Credit: zmescience.com
Map of the Earth showing fault lines (blue) and zones of volcanic activity (red). Credit: zmescience.com

It raises the level of the world’s oceans towards the equator. Without this gravity, the oceans would redistribute, raising levels at the poles. It has also slowed Earth’s rotation on its axis. Shortly after its formation, the Earth turned once every 6 hours. Without that Moon to slow us down, we’d have much more severe weather.

It stabilizes the Earth’s rotation on its axis. It’s possible that the Earth might have rolled over on its axis on a regular basis, causing a complete redistribution of the Earth’s water. Astronomers think this happened on Mars, because it never had a large Moon to stabilize it.

But the biggest impact that the Moon has on life is through tides. That regular movement of water that exposes the land at the edge of the ocean, and then covers it again just a few hours later. This could have encouraged life to adapt and move from the oceans to land.

One of the most subtle effects from the Moon is what it has done to life itself. Nocturnal animals behave differently depending on where the Moon is in the sky during its 29.5-day cycle. When the Moon is full and bright, prey fish stay hidden in the reef, when they’d be most visible.

Prey fish in the reef. Credit: Laslo Ilyes
Prey fish in the reef. Credit: Laslo Ilyes

Amazingly, lions are less likely to hunt during the full Moon, and researchers have found that lion attacks on humans happen 10 days after the full Moon, and many bats will be less active during the full Moon.

With so many species on Earth affected by the Moon, it’s reasonable to think that there would have been a different evolutionary direction for life on Earth over the eons, and humans might never have evolved.

It looks like the Moon is important after all. Important to the geology of Earth, and important to the evolution of life itself.

As extrasolar planet hunters search for new worlds, and determine their viability for life, they might want to focus on the worlds with moons first.

What impact has the Moon had on your life? Post your anecdotes in the comments!

Weekly Space Hangout – Oct. 9, 2015: Nobel Prizes, Private Moon Launches & Water on Pluto!

Host: Fraser Cain (@fcain)

Guests:
Paul Sutter (pmsutter.com / @PaulMattSutter)
Morgan Rehnberg (cosmicchatter.org / @MorganRehnberg )
Kimberly Cartier (@AstroKimCartier )
Brian Koberlein (@briankoberlein / briankoberlein.com)
Continue reading “Weekly Space Hangout – Oct. 9, 2015: Nobel Prizes, Private Moon Launches & Water on Pluto!”

Weekly Space Hangout – Oct 2, 2015: Water on Mars, Blood Moon Eclipses, and More Pluto!

Host: Fraser Cain (@fcain)

Guests:

Morgan Rehnberg (cosmicchatter.org / @MorganRehnberg )
Pamela Gay (cosmoquest.org / @cosmoquestx / @starstryder)
Kimberly Cartier (@AstroKimCartier )
Brian Koberlein (@briankoberlein / briankoberlein.com)
Alessondra Springmann (@sondy)
Continue reading “Weekly Space Hangout – Oct 2, 2015: Water on Mars, Blood Moon Eclipses, and More Pluto!”

Do Astronauts Drink their Pee?

Do Astronauts Drink their Pee?

In order to fly in space, astronauts need to make a few sacrifices, like drink their own urine. Yuck? Don’t worry, it’s totally safe.

Astronauts are a resourceful bunch. They’re the best of the best of the best of the best. They’re ready to do whatever it takes to get the job done. WHATEVER IT TAKES, INCLUDING DRINKING PEE. They live on the International Space Station for the better part of a year, where air, food and water are precious resources. Sometimes you take a hit for the team back.

Every drop of water on the International Space Station was carried there from Earth, by rocket, possibly in someone’s bladder. The cost of launching a single kilo into orbit can be over $10 grand. Do a little back of the tp math and the value of a single kilogram of water in space is worth almost as much as a kilogram of yellow gold here on Earth.

That’s actual money gold, and not pee joke gold. The punchline is astronauts need to conserve water. For the longest time, there wasn’t any way to take conservation to the “next level”. All the “waste water” including pee produced on the station was just held, possibly uncomfortably and resulting in dancing, and it needed to be disposed of.

In 2009, NASA got serious about conserving water and launched the Water Recovery System to the International Space Station. What is it with you guys and names? I would have shot for “Precycling Internal Solution System” just for the acronym. In fact, that’s what we’re using now.

Ever since, astronauts have been drinking their own urine like Captain Redbeard Rum on Blackadder. Generally after it’s been purified by the recovery system, or if you prefer “peecycled”. Outside of that I’m sure accidents happen, and whatever they get up to in their own time is their business.

Speaking of which, Here’s a video of beloved Canadian astronaut Chris Hadfield demonstrating the P.I.S.S system. It takes all water vapor, sweat, and grey water produced and excreted by astronauts and turns it back into drinkable water.

On Earth, you can clear dirty water by boiling it. Collect your steam on a cold surface, pure, pee free and ready for drinking again. Pro tip, this process actually requires gravity, which isn’t readily available when you’re in free fall.

The Recovery System looks like a big spinning keg, which creates artificial gravity. It’s heated and steam is produced. Dirt and contaminants such as the most purified pee molecules are pushed to the edges of the drum while the steam is carried away.

NASA's Water Recovery System. Credit: NASA
NASA’s Water Recovery System. Credit: NASA

The artificial gravity isn’t perfect, and only 93% of the water can be recovered this way. This means that dirty waste water builds up inside the space station and needs to be flushed with the rest of the trash. Astronauts can’t peecycle everything on the space station, trash does build up. They’ve got a solution for this too.

The most recent cargo delivery spacecraft is always left attached to the space station. Instead of doing laundry, which would use up their precious water and is super boring. Seriously, if you went to the trouble of sending me to space and asked to me wash my clothes I’d get a little snippy.

Astronauts do what the rest of us only dream about. They just wear their clothes until they’re totally worn out. Then throw their laundry into the excess module. Once it’s completely filled with pee, laundry, food remnants, and other, uh… stuff, the spacecraft detaches from the station and re-enters the Earth’s atmosphere where it’s incinerated. No fuss, no muss. Also, clearly for this episode, we’re only going as far as pee jokes as poop jokes are off the table.

Yes, astronauts are drinking their pee. They close their eyes and remind themselves it’s just pure water. Completely safe and delicious to drink. No pee molecules left here. As astronaut Koichi Wakata said, “Here on board the ISS, we turn yesterday’s coffee into tomorrow’s coffee”.

Would you be willing to drink the water produced by the Water Recovery System? Tell us in the comments below.

This Mountain on Mars Is Leaking

Seasonal flows spotted by HiRISE on northwestern slopes in Hale Crater. (NASA/JPL/University of Arizona)

As the midsummer Sun beats down on the southern mountains of Mars, bringing daytime temperatures soaring up to a balmy 25ºC (77ºF), some of their slopes become darkened with long, rusty stains that may be the result of water seeping out from just below the surface.

The image above, captured by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter on Feb. 20, shows mountain peaks within the 150-km (93-mile) -wide Hale Crater. Made from data acquired in visible and near infrared wavelengths the long stains are very evident, running down steep slopes below the rocky cliffs.

These dark lines, called recurring slope lineae (RSL) by planetary scientists, are some of the best visual evidence we have of liquid water existing on Mars today – although if RSL are the result of water it’s nothing you’d want to fill your astro-canteen with; based on the first appearances of these features in early Martian spring any water responsible for them would have to be extremely high in salt content.

According to HiRISE Principal Investigator Alfred McEwen “[t]he RSL in Hale have an unusually “reddish” color compared to most RSL, perhaps due to oxidized iron compounds, like rust.”

See a full image scan of the region here, and watch an animation of RSL evolution (in another location) over the course of a Martian season here.

Perspective view of Hale crater made from data acquired by ESA's Mars Express. Credit: ESA/DLR/FU Berlin (G. Neukum)
Perspective view of Hale crater made from data acquired by ESA’s Mars Express. Credit: ESA/DLR/FU Berlin (G. Neukum)
Channels in the southeastern ejecta of Hale crater. Credit: NASA/JPL-Caltech/Arizona State University. (Source.)
THEMIS image of channels in the southeastern ejecta of Hale crater. Credit: NASA/JPL-Caltech/Arizona State University. (Source.)

Hale Crater itself is likely no stranger to liquid water. Its geology strongly suggests the presence of water at the time of its formation at least 3.5 billion years ago in the form of subsurface ice (with more potentially supplied by its cosmic progenitor) that was melted en masse at the time of impact. Today carved channels and gullies branch within and around the Hale region, evidence of enormous amounts of water that must have flowed from the site after the crater was created. (Source.)

The crater is named after George Ellery Hale, an astronomer from Chicago who determined in 1908 that sunspots are the result of magnetic activity.

Read more on the University of Arizona’s HiRISE site here.

Sources: NASA, HiRISE and Alfred McEwen

UPDATE April 13: Conditions for subsurface salt water (i.e., brine) have also been found to exist in Gale Crater based on data acquired by the Curiosity rover. Gale was not thought to be in a location conducive to brine formation, but if it is then it would further strengthen the case for such salt water deposits in places where RSL have been observed. Read more here.

Mars Loses an Ocean But Gains the Potential for Life

NASA scientists have determined that a primitive ocean on Mars held more water than Earth's Arctic Ocean and that the Red Planet has lost 87 percent of that water to space. Credit: NASA/GSFC

It’s hard to believe it now looking at Mars’ dusty, dessicated landscape that it once possessed a vast ocean. A recent NASA study of the Red Planet using the world’s most powerful infrared telescopes clearly indicate a planet that sustained a body of water larger than the Earth’s Arctic Ocean.

If spread evenly across the Martian globe, it would have covered the entire surface to a depth of about 450 feet (137 meters). More likely, the water pooled into the low-lying plains that cover much of Mars’ northern hemisphere. In some places, it would have been nearly a mile (1.6 km) deep. 

Three of the best infrared observatories in the world were used to study normal to heavy water abundances in Mars atmosphere, especially the polar caps, to create a global map of the planet's water content and infer an ancient ocean. Credit: NASA/ GSFC
Three of the best infrared observatories in the world were used to study normal to heavy water abundances in Mars atmosphere, especially the polar caps, to create a global map of the planet’s water content and infer an ancient ocean. Credit: NASA/ GSFC

Now here’s the good part. Before taking flight molecule-by-molecule into space, waves lapped the desert shores for more than 1.5 billion years – longer than the time life needed to develop on Earth. By implication, life had enough time to get kickstarted on Mars, too.

A hydrogen atom is made up of one proton and one electron, but its heavy form, called deuterium, also contains a neutron. HDO or heavy water is rare compared to normal drinking water, but being heavier, more likely to stick around when the lighter form vaporizes into space. Credit: NASA/GFSC
A hydrogen atom is made up of one proton and one electron, but its heavy form, called deuterium, also contains a neutron. HDO or heavy water is rare compared to normal drinking water, but being heavier, more likely to stick around when the lighter form vaporizes into space. Credit: NASA/GFSC

Using the three most powerful infrared telescopes on Earth – the W. M. Keck Observatory in Hawaii, the ESO’s Very Large Telescope and NASA’s Infrared Telescope Facility – scientists at NASA’s Goddard Space Flight Center studied water molecules in the Martian atmosphere. The maps they created show the distribution and amount of two types of water – the normal H2O version we use in our coffee and HDO or heavy water, rare on Earth but not so much on Mars as it turns out.

Maps showing the distribution of H20 and HDO across the planet made with the trio of infrared telescopes. Credit: NASA/GSFC
Maps showing the distribution of H20 and HDO (heavy water) across the planet made with the trio of infrared telescopes. Credit: NASA/GSFC

In heavy water, one of the hydrogen atoms contains a neutron in addition to its lone proton, forming an isotope of hydrogen called deuterium. Because deuterium is more massive than regular hydrogen, heavy water really is heavier than normal water just as its name implies. The new “water maps” showed how the ratio of normal to heavy water varied across the planet according to location and season. Remarkably, the new data show the polar caps, where much of Mars’ current-day water is concentrated, are highly enriched in deuterium.

It's thought that
It’s thought that the decay of Mars’ once-global magnetic field, the solar wind stripped away much of the planet’s early, thicker atmosphere, allowing solar UV light to break water molecules apart. Lighter hydrogen exited into space, concentrating the heavier form. Some of the hydrogen may also departed due to the planet’s weak gravity. Credit: NASA/GSFC

On Earth, the ratio of deuterium to normal hydrogen in water is 1 to 3,200, but at the Mars polar caps it’s 1 to 400.  Normal, lighter hydrogen is slowly lost to space once a small planet has lost its protective atmosphere envelope, concentrating the heavier form of hydrogen. Once scientists knew the deuterium to normal hydrogen ratio, they could directly determine how much water Mars must have had when it was young. The answer is A LOT!

Goddard scientists estimate that only 13% of Mars' original water reserves are still around today, concentrated in the icy polar caps. The rest took off for space. Credit: NASA/GSFC
Goddard scientists estimate that only 13% of Mars’ original water reserves are still around today, concentrated in the icy polar caps. The rest took off for space. Credit: NASA/GSFC

Only 13% of the original water remains on the planet, locked up primarily in the polar regions, while 87% of the original ocean has been lost to space. The most likely place for the ocean would have been the northern plains, a vast, low-elevation region ideal for cupping huge quantities of water. Mars would have been a much more earth-like planet back then with a thicker atmosphere, providing the necessary pressure, and warmer climate to sustain the ocean below.

Mars at the present time has little to no liquid water on its cold, desert-like surface. Long ago, the Sun saw its reflection from wave-rippled lakes and a northern ocean. Credit: NASA/GSFC
Mars at the present time has little to no liquid water on its cold, desert-like surface. Long ago, the Sun almost certainly saw its reflection from wave-rippled lakes and a northern ocean. Credit: NASA/GSFC

What’s most exciting about the findings is that Mars would have stayed wet much longer than originally thought. We know from measurements made by the Curiosity Rover that water flowed on the planet for 1.5 billion years after its formation. But the new study shows that the Mars sloshed with the stuff much longer. Given that the first evidence for life on Earth goes back to 3.5 billion years ago – just a billion years after the planet’s formation – Mars may have had time enough for the evolution of life.

So while we might bemoan the loss of so wonderful a thing as an ocean, we’re left with the tantalizing possibility that it was around long enough to give rise to that most precious of the universe’s creations – life.

To quote Charles Darwin: “… from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

Illustration showing Mars evolving from a wet world to the present-day Red Planet. Credit: NASA/GSFC
Illustration showing Mars evolving from a wet world to the present-day where liquid water can’t pond on its surface without vaporizing directly into the planet’s thin air. As Mars lost its atmosphere over billions of years, the remaining water, cooled and condensed to form the north and south polar caps. Credit: NASA/GSFC

Why Don’t We Search for Different Life?

Why Don’t We Search for Different Life?

If we really want to find life on other worlds, why do we keep looking for life based on carbon and water? Why don’t we look for the stuff that’s really different?

In the immortal words of Arthur C. Clarke, “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”

I’m seeking venture capital for a Universal buffet chain, and I wondering if I need to include whatever the tentacle equivalent of forks is on my operating budget. If there isn’t any life, I’m going to need to stop watching so much science fiction and get on with helping humanity colonize space.

Currently, astrobiologists are hard at work searching for life, trying to answer this question. The SETI Institute is scanning radio signals from space, hoping to catch a message. Since humans use radio waves, maybe aliens will too. NASA is using the Curiosity Rover to search for evidence that liquid water existed on the surface of Mars long enough for life to get going. The general rule is if we find liquid water on Earth, we find life. Astronomers are preparing to study the atmospheres of extrasolar planets, looking for gasses that match what we have here on Earth.

Isn’t this just intellectually lazy? Do our scientists lack imagination? Aren’t they all supposed to watch Star Trek How do we know that life is going to look anything like the life we have on Earth? Oh, the hubris!

Who’s to say aliens will bother to communicate with radio waves, and will transcend this quaint transmission system and use beams of neutrinos instead. Or physics we haven’t even discovered yet? Perhaps they talk using microwaves and you can tell what the aliens are saying by how your face gets warmed up. And how do we know that life needs to depend on water and carbon? Why not silicon-based lifeforms, or beings which are pure energy? What about aliens that breathe pure molten boron and excrete seahorse dreams? Why don’t these scientists expand their search to include life as we don’t know it? Why are they so closed-minded?

Viking Lander
In 1976, two Viking spacecraft landed on Mars. The image is of a model of the Viking lander, along with astronomer and pioneering astrobiologist Carl Sagan. Each lander was equipped with life detection experiments designed to detect life based on its metabolic activities.
Credits: NASA/Jet Propulsion Laboratory, Caltech

The reality is they’re just being careful. A question this important requires good evidence. Consider the search for life on Mars. Back in the 1970s, the Viking Lander carried an experiment that would expose Martian soil to water and nutrients, and then try to detect out-gassing from microbes. The result of the experiment was inconclusive, and scientists still argue over the results today. If you’re going to answer a question like this, you want to be conclusive. Also, getting to Mars is pretty challenging to begin with. You probably don’t want to “half-axe” your science.

The current search for life is incremental and exhaustive. NASA’s Spirit and Opportunity searched for evidence that liquid water once existed on the surface of Mars. They found evidence of ancient water many times, in different locations. The fact that water once existed on the surface of Mars is established. Curiosity has extended this line of research, looking for evidence that water existed on the surface of Mars for long periods of time. Long enough that life could have thrived. Once again, the rover has turned up the evidence that scientists were hoping to see. Mars was once hospitable for life, for long periods of time. The next batch of missions will actually search for life, both on the surface of Mars and bringing back samples to Earth so we can study them here.

The search for life is slow and laborious because that’s how science works. You start with the assumption that since water is necessary for life on Earth, it makes sense to just check other water in the Solar System. It’s the low hanging fruit, then once you’ve exhausted all the easy options, you get really creative.

An illustration of a Titanic lake by Ron Miller. All rights reserved. Used with permission.
An illustration of a Titanic lake by Ron Miller. All rights reserved. Used with permission.

Scientists have gotten really creative about how and where they could search for life. Astrobiologists have considered other liquids that could be conducive for life. Instead of water, it’s possible that alternative forms of life could use liquid methane or ammonia as a solvent for its biological processes. In fact, this environment exists on the surface of Titan. But even if we did send a rover to Titan, how would we even know what to look for?

We understand how life works here, so we know what kinds of evidence to pursue. But kind of what evidence would be required to convince you there’s life as you don’t understand it? Really compelling evidence.
Go ahead and propose some alternative forms of life and how you think we’d go searching for it in the comments.

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