Ejercicio de la Soberanía del Pueblo

A PICTURESQUE LANDSCAPE A PICTURESQUE LANDSCAPE From the first images, Huygens forever From the first images, Huygens forever changed scientists’ understanding of Titan. changed scientists’ understanding of Titan. Its pictures showed riverbeds — channels Its pictures showed riverbeds — channels cut clearly into Titan’s face. These rivers cut clearly into Titan’s face. These rivers show

showed drainage networks similar ed drainage networks similar to thoseto those found all over Earth: small

found all over Earth: small channels feed-channels feed- ing into larger rivers, which empty out into ing into larger rivers, which empty out into flat deltas.

flat deltas.

Bright highlands showed rough, jagged Bright highlands showed rough, jagged terrain. Steep river valleys and

terrain. Steep river valleys and canyonscanyons indicated that Titan’s rivers could be prone indicated that Titan’s rivers could be prone to flooding, a

to flooding, and likewise showed signs ofnd likewise showed signs of methane rain erosion. Other riverbeds methane rain erosion. Other riverbeds hinted at gentler streams. Scientists think hinted at gentler streams. Scientists think these are fed not by rainfa

these are fed not by rainfall but fromll but from “spring sapping,” where liquid methane “spring sapping,” where liquid methane wells up through the ground.

wells up through the ground.

Closer up, Huygens took stock of its Closer up, Huygens took stock of its landing site. The probe touched down on a landing site. The probe touched down on a dark plain. While it saw no sign of current dark plain. While it saw no sign of current surface liquid, the region strongly resem- surface liquid, the region strongly resem- bled a dried lake bed or f

bled a dried lake bed or f loodplain.loodplain. Scattered around Huygens’ base were cob- Scattered around Huygens’ base were cob- blestones, edges rounded as if shaped by blestones, edges rounded as if shaped by flowing liquid. The stones are of a simil flowing liquid. The stones are of a simil arar

This progression of vistas from four different altitudes, from highest (top) This progression of vistas from four different altitudes, from highest (top) to lowest (bottom), shows flattened (Mercator) projections of the moon to lowest (bottom), shows flattened (Mercator) projections of the moon as Huygens punched through Titan’s haze to reveal its strangely Earth-like as Huygens punched through Titan’s haze to reveal its strangely Earth-like surface features.

surface features.ESA/NASA/JPL/UNIVERSITY OF ARIZONAESA/NASA/JPL/UNIVERSITY OF ARIZONA

A 360° mosaic of images snapped from about 5 miles (8 km) above Titan’s surface shows a plateau (center) and Huygens’ A 360° mosaic of images snapped from about 5 miles (8 km) above Titan’s surface shows a plateau (center) and Huygens’ eventual landing site (darker area on the right side of the image). This image and other data from the probe have been used eventual landing site (darker area on the right side of the image). This image and other data from the probe have been used to determine that the wind speed in Titan’s atmosphere was about 4 mph (6–7 km/h).

to determine that the wind speed in Titan’s atmosphere was about 4 mph (6–7 km/h). NASA/JPL/ESA/UNIVERSITY OF ARIZONANASA/JPL/ESA/UNIVERSITY OF ARIZONA

Huygens’ final resting Huygens’ final resting place is estimated to place is estimated to fall within the white fall within the white circle on this image circle on this image taken with the probe’s taken with the probe’s Descent Imager/  Descent Imager/  Spectral Radiometer. Spectral Radiometer. NASA/JPL/ESA/UNIVERSITY NASA/JPL/ESA/UNIVERSITY OF ARIZONA OF ARIZONA

The Huygens probe showed a landscape shaped The Huygens probe showed a landscape shaped by the flow of liquid on Titan’s surface, such as by the flow of liquid on Titan’s surface, such as this drainage system thought to channel liquid this drainage system thought to channel liquid methane runoff into a larger river.

methane runoff into a larger river.NASA/JPL/ESA/NASA/JPL/ESA/ UNIVERSITY OF ARIZONA

UNIVERSITY OF ARIZONA

100 miles (150 km)

100 miles (150 km)

S

Soouutthh WWeesstt NNoorrtthh EEaasstt SSoouutthh

10 miles (15 km) 10 miles (15 km) 1.2 miles (2 km) 1.2 miles (2 km) 0.25 miles (0.4 km) 0.25 miles (0.4 km)

54

54 A S T R O N O M YA S T R O N O M Y _••  M A R C H 2 0 1 8  M A R C H 2 0 1 8

size, implying that the sa

size, implying that the same currents mightme currents might have moved all of them, but scientists have moved all of them, but scientists remain unsure whether this is the ca remain unsure whether this is the ca se.se.

Hayes points out that the rounded cob- Hayes points out that the rounded cob- bles near Huygens’ landing site appear like bles near Huygens’ landing site appear like stones ground smooth by a river carrying stones ground smooth by a river carrying them over distance. But on Earth, a river them over distance. But on Earth, a river drops larger stones earlier in its path, then drops larger stones earlier in its path, then smaller stones as the flow begins to peter smaller stones as the flow begins to peter out. “What intrigues me personally,” out. “What intrigues me personally,” Hayes says, “is that in the decade since Hayes says, “is that in the decade since those images and data were taken, we those images and data were taken, we started to question everything, or find started to question everything, or find that every answer you get leads to three that every answer you get leads to three new questions.”

new questions.”

Huygens quite literally scratched Titan’s Huygens quite literally scratched Titan’s surface. And by opening up an entire new surface. And by opening up an entire new world to researchers, it also jump-started a world to researchers, it also jump-started a new generation of research, inviting ques- new generation of research, inviting ques- tions by the thousands. Scientists then and tions by the thousands. Scientists then and now look to Huygens as the only eyewit- now look to Huygens as the only eyewit- ness to an entire complex world, but stud- ness to an entire complex world, but stud- ies are limited by the short time and tiny ies are limited by the short time and tiny area the probe could

area the probe could explore.explore.

So far from the Sun and under Titan’s So far from the Sun and under Titan’s hazy skies, Huygens took its pictures in a hazy skies, Huygens took its pictures in a twilight sort

twilight sort of lighting. At one point, itsof lighting. At one point, its  vision incl

 vision included a dewuded a dewdrop that formed odrop that formed onn the probe’s exterior. While probably the probe’s exterior. While probably induced by Huygens itself and the heat induced by Huygens itself and the heat from its landing, the single drop was from its landing, the single drop was none-none- theless the first

theless the first in situin situ _{sighting of liquid on sighting of liquid on} a world other than Earth.

a world other than Earth.

COLLECTING GASES

COLLECTING GASES

On its way down, Huygens sampled the On its way down, Huygens sampled the gases circulating in Titan’s atmosphere and gases circulating in Titan’s atmosphere and confirmed they were mostly nitrogen and confirmed they were mostly nitrogen and methane. More importantly, it measured methane. More importantly, it measured

the temperature, pressure, and abundance the temperature, pressure, and abundance of gases from the atmosphere’s top all the of gases from the atmosphere’s top all the way to the

way to the ground, creating a one-dimen-ground, creating a one-dimen- sional map of Titan’s skies. It revealed high sional map of Titan’s skies. It revealed high levels of stratification, passing from one levels of stratification, passing from one zone to another as it fell.

zone to another as it fell.

One of Huygens’ goals was to hunt for One of Huygens’ goals was to hunt for noble gases, such as argon. Noble gases are noble gases, such as argon. Noble gases are chemically disinclined to join with ot chemically disinclined to join with ot herher elements to form compounds, so their elements to form compounds, so their abundances hint at long histories, stretch- abundances hint at long histories, stretch- ing back to the availability of these gases at ing back to the availability of these gases at the birth

the birth of the solar system. Their pres-of the solar system. Their pres- ence helps scientists understand how ence helps scientists understand how Titan’s atmosphere came to be — and, like- Titan’s atmosphere came to be — and, like- wise, how other wor

wise, how other worlds like Earlds like Earth mightth might have attained similar

have attained similar thick atmospheres.thick atmospheres. But Huygens, despite descending quite But Huygens, despite descending quite literally through the thick of things, literally through the thick of things, detected low abundances of argon com- detected low abundances of argon com- pared with nitrogen, especially a particular pared with nitrogen, especially a particular isotope known as argon-36. Huygens found isotope known as argon-36. Huygens found it roughly a mil

it roughly a mil lion times less abundantlion times less abundant than in t

than in the Sun, implhe Sun, implying that Titan couldying that Titan could not have gathered its atmosphere directly not have gathered its atmosphere directly from the early solar nebula. Instead, its from the early solar nebula. Instead, its atmosphere was likely delivered by bom- atmosphere was likely delivered by bom- bardments of space rocks, bolstering the bardments of space rocks, bolstering the case for Eart

case for Earth’s atmosphh’s atmosphere forming in theere forming in the same way.

same way.

On the other hand, detection of another On the other hand, detection of another isotope, argon-40, tells a

isotope, argon-40, tells a different story.different story. This isotope arises from the radioactive This isotope arises from the radioactive decay of potassium found in rocks. For decay of potassium found in rocks. For Huygens to sniff out such a gas in the Huygens to sniff out such a gas in the atmosphere implies that Titan must have a atmosphere implies that Titan must have a way to release it: an active geologic, or at way to release it: an active geologic, or at least cryologic, cycle where rocks or ice are least cryologic, cycle where rocks or ice are churned from Titan’s depths to its surface churned from Titan’s depths to its surface

and atmosphere, and released by ice volca- and atmosphere, and released by ice volca- noes. But whether this process is powered noes. But whether this process is powered by Titan’s own internal heating mecha- by Titan’s own internal heating mecha- nisms, by the heat of Saturn’s tidal pull, or nisms, by the heat of Saturn’s tidal pull, or even if the process truly exists at all is still even if the process truly exists at all is still under debate.

under debate. While Voyager’

While Voyager’s original s original methane dis-methane dis- covery had raised the faint specter of a covery had raised the faint specter of a lienlien biology as its origin,

biology as its origin, HuygeHuygens laid tns laid thesehese hopes mostly to rest. Scientists knew that hopes mostly to rest. Scientists knew that some kind of activity must refresh Titan’s some kind of activity must refresh Titan’s methane stores, or else sunl

methane stores, or else sunlight wouldight would destroy the gas in a

destroy the gas in a matter of a few millionmatter of a few million years. But the a

years. But the arrangemenrrangement of methanet of methane layers in Titan’s atmosphere, coupled with layers in Titan’s atmosphere, coupled with the carbon

the carbon isotopes Huygeisotopes Huygens sampled,ns sampled, indicated once again that geologic pro- indicated once again that geologic pro- cesses were the likely methane source. cesses were the likely methane source.

However, in Titan’s haze layers, However, in Titan’s haze layers, Huyge

Huygens detected molecules similar ns detected molecules similar toto tholins produced in earthly

tholins produced in earthly laboratorilaboratories.es. Tholins are thought to be important to t Tholins are thought to be important to t hehe development of life on Earth, and the com- development of life on Earth, and the com- plex carbon molecules are a

plex carbon molecules are a source ofsource of active research. Their presence on Titan is active research. Their presence on Titan is an encouraging sign that the building an encouraging sign that the building blocks of life are not unique t

blocks of life are not unique to Earto Earth.h.