Astronomy

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Revealing Pluto’s first officially named features

After an amazing 20 years in space —

13 of those years at Saturn — NASA’s

venerable Cassini spacecraft met its

fiery death in the upper atmosphere

of the ringed planet September 15.

The craft was launched October 15,

1997. Gravity assists from Venus,
      Earth, and Jupiter sent it on to Saturn,
      where it arrived in June 2004. From
      there, the craft wrote the book on our
      understanding of the Saturn system.
      It provided incredible views of
      Saturn’s largest moon, Titan, showing
      ever-shifting seas of hydrocarbons
      and revealing a subsurface ocean
      much like Europa’s.
      Cassini also followed up on tenta-
      tive evidence from the Voyager
      probes of watery activity on the small
      moon Enceladus, ultimately discover-
      ing geysers shooting water hundreds
      of miles into space. Their source is a

global subsurface ocean, elevating

the moon to one of the more likely

places in the solar system to find

alien life. The spacecraft also discov-

ered circumstantial evidence of

oceans and cryovolcanism on Dione,

as well as inexplicable red streaks on

Tethys that might be due to outgas-

sing, fracturing, or perhaps some

other process entirely.

In its final months, Cassini skimmed

Saturn’s rings and traversed the space

between the rings and the planet itself.

Using a last gravity assist from Titan,

NASA set Cassini on a destruction

course to disintegrate within minutes in

Saturn’s atmosphere. The decision was

made out of concern that extreme

bacterial life from Earth could survive

deep inside the craft and contaminate

one of the system’s habitable moons

if an accident were ever to occur.

The spacecraft’s signal went out at

4:55:46 A.M. PDT, to a standing

ovation. Shortly after, Cassini

program manager Earl Maize told his

team, “I hope you’re all deeply proud

of this amazing accomplishment.”

Linda Spilker, a Cassini project

scientist who has been with the

mission since it was first planned in

1982, said, “It felt so much like losing

a friend, a spacecraft I got to know

so well.”

NASA is now reviewing proposals

for future missions that could return

us to Titan, Enceladus, or Saturn. In

the meantime, there are several

hundred gigabytes of data for

present and future generations to

sort through to make amazing

discoveries about the Saturn system.

Thanks for everything, Cassini.

— J.W.

QUICK TAKES

TAKING AIM

NASA plans to use the James

Webb Space Telescope to

study plume activity on the

icy solar system worlds

Europa and Enceladus.

• MOON PILEUP
  Uranus’ satellites
  Desdemona and Cressida are
  on a future collision course
  as Cressida destabilizes its
  sister moon’s orbit.
  REFLECTION •
  PERFECTION
  Gradually applying atom-
  thin coatings could improve
  silver-based telescope mir-
  rors by preventing corrosion.


• 
  

  LARGE SURVEY
  The Karl Jansky Very Large
  Array in New Mexico is
  undertaking its biggest-ever
  observing campaign, search-
  ing the sky for high-energy
  events over the next 7 years.

  
  


• 
  

  FAST AND FURIOUS
  Astronomers estimate that
  one or more mysterious
  fast radio bursts may pop off
  every second somewhere
  in the universe.
  SLEEPING BEAUTY•
  NASA’s New Horizons awoke
  from a five-month slumber
  September 12, en route
  to MU 69 — a primordial
  Kuiper Belt object.
  SPIN DOCTORS•
  Researchers seeking to
  understand galaxy shapes
  now believe a galaxy’s
  rotation speed plays a big
  role in its appearance.

  
  


• 
  

  SEVEN SISTERS
  The Pleiades’ seven recog-
  nizable stars are all variable,
  according to evidence from
  the Kepler telescope.

  
  


• 
  

  ALIEN AGENTS
  Comets and asteroids of
  interstellar origin may have
  brought the building blocks
  of DNA to Earth. — J.W.

  
  

NOT SO WINDY. New ALMA observations of young galaxies indicate that the winds generated by new stars aren’t

strong enough to blow away material and stop star formation.

Cassini probe sends its last regards

42

The number of

spacecraft that

ended their

missions on

another planet,

excluding moons.

NASA/JHUAPL/S

WRI/ROSS BEYER

THE ULTIMATE BREAKUP. Cassini disappeared into Saturn on September 15, ending its 13-year-long mission at the ringed planet.

Before breaking up, the spacecraft beamed back valuable data from within the planet’s atmosphere. NASA/JPL-CALTECH

MAPMAKING. New Horizons gave us our first and only up-close look at the Pluto system in 2015. In September, the International

Astronomical Union (IAU) announced the first 14 officially named features on the dwarf planet. The names highlight individuals whose

work has contributed to our understanding of Pluto, including Clyde Tombaugh and James Elliot. Some names also pay homage to

famous explorers and space missions, such as Sir Edmund Hillary and Sputnik 1. Additional regions bear the names of figures or places

associated with the underworld in Norse, Australian, Inuit, and Greek mythology. The IAU will continue to consider proposals to name

more features on Pluto and its five moons. — A.K.

Tombaugh

Regio

Voyager Terra Hayabusa Terra

Burney

crater

Djanggawul

Fossae

Elliot crater

Te nz ing

Montes

Adlivun

Cavus

Hillary

Montes

Al-Idrisi Montes

Sleipnir Fossae

Virgil Fossae

Tar t arus

Dorsa

Sputnik

Planitia