Pluto’s mountains have methane snowcaps, New Horizons images Quaoar
Snowcaps similar to those on Earth are visible in the southernmost region at the left of Pluto’s encounter hemisphere, according to the latest images sent back by New Horizons. However, unlike the water-ice caps of Earth, these are composed of methane.
While they appear on the bottom edge of the spacecraft’s images, the methane snowcaps are actually located just below the dark equatorial region known as Cthulhu Regio, southwest of Sputnik Planum, the nitrogen ice plain that constitutes the left side of Pluto’s “heart” feature.
In recognition of Sputnik Planum’s low elevation, mission scientists have begun referring to the region as Sputnik Planitia.
New Horizons’ science instruments identified the ice topping the chain of bright mountains as atmospheric methane rather than water. Because of the mountains’ high elevation, atmospheric methane condenses into frost on their surfaces.
The mountain chain, which extends north, reaching into Cthulhu Regio, is interspersed with sharp valleys, each of which stretches tens of miles long and several miles across.
North is up in this New Horizons image. The southwestern valleys are marked with white arrows.
Visible in the rolling plains at the eastern section of this area is a similar, branched system of smaller valleys. Because the valleys lead into the plains region, scientists believe this area may have once been covered with flowing nitrogen ice.
If Sputnik Planum’s ice was once at a higher elevation than it is today, that flowing ice could have formed the valley network, which in the New Horizons image is highlighted with blue arrows.
Also visible in the middle area of the region are wide, deep flat-floored depressions irregularly spaced with widths more than 50 miles (80 kilometers) across and depths of nearly two miles (3 kilometers). These are marked with green arrows.
Based on these depressions’ widths and depths, scientists think they formed through surface collapse rather than ice sublimation.
This entire area’s wide range of geological terrains may hold clues to the regions that New Horizons could not image because they were hidden in darkness during the flyby.
New Horizon’s Multispectral Visible Imaging Camera (MVIC) captured this false-color image from a distance of about 21,100 miles (33,900 kilometers) approximately 45 minutes before closest approach to Pluto on July 14, 2015. Its resolution is about 2,230 feet (680 meters) per pixel.
On July 13–14, 2016, exactly a year after the encounter, New Horizons, now much further in the Kuiper Belt and speeding toward its Jan. 1, 2019, rendezvous with KBO 2014 MU69, successfully imaged another dwarf planet, Quaoar, using its Long Range Reconnaissance Imager (LORRI).
Composite photos made up of 24 individual LORRI images were taken at four separate times during this two-day period, with a total exposure of 239 seconds.
The composites were then put together to create an animation showing the 690-mile (1,100-kilometer) Quaoar moving against background stars, with individual composites identified on the upper left in red letters as A, B, C, and D.
About half the size of Pluto, Quaoar, discovered in 2002, was approximately 1.3 billion miles (2.1 billion kilometers) from New Horizons and around four billion miles (6.4 billion kilometers) from the Sun when the images were taken.
From that distance, LORRI was able to see only part of Quaoar’s illuminated surface in contrast to Earth-based telescopes, which are capable of observing it wholly illuminated.
As the only probe in the Kuiper Belt, New Horizons is able to image its objects from a unique perspective. Scientists can compare photos of objects like Quaoar captured from Earth to those imaged by New Horizons to determine how these objects scatter light on their surfaces.
Two distant galaxies, IC 1048 and UGC 09485, are visible in the background of the LORRI image, as are many stars. The galaxies are estimated to each be about 370 billion times farther from the spacecraft than Quaoar.
In the animation, viewers can see Quaoar move against these much more distant stars and galaxies. New Horizons scientists note any other objects that appear to move are camera artifacts and not actual objects.
Insights on Pluto
Members of the New Horizons team have continued to share their experiences and insights gained from working on the mission in a series of blog entries.
In “Twenty-Six Years and Three Billion Miles to Pluto“, mission scientist Fran Bagenal of the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder discusses the many questions people ask about Pluto during her public presentations.
Bagenal recounts the long journey that started in 1989 when now mission principal investigator Alan Stern first suggested sending a spacecraft to Pluto. She noted the significance of digital photography, which made it possible to image distant Kuiper Belt Objects.
Mission scientist Anne Verbiscer of the University of Virginia notes Pluto reached its annual opposition point July 8 when it appeared on the opposite side of the sky as the Sun.
In “Pluto: Preparing for the Perfect Alignment“, Verbiscer reported that in 2018, Pluto and Charon will be in a near-perfect alignment with the Earth and Sun, presenting a unique opportunity to capture images of their surfaces and compare these with photos taken by New Horizons.
Such comparisons will help scientists learn more about the physical properties of both objects’ surfaces by studying the way those surfaces scatter sunlight.
Ralph instrument co-principal investigator Cathy Olkin and Ralph engineer Eddie Weigle take readers behind the scenes in “Commanding the Eyes of New Horizons“.
Olkin and Weigle detail the process of loading commands to the Ralph instrument, which serves as the spacecraft’s “eyes”, transmitting the commands across the Solar System through NASA’s Deep Space Network, and making sure they are accurately carried out.
Project scientist Hal Weaver, in “Pluto: What A Journey!“, takes readers through efforts of the pre-launch years to develop a spacecraft and instruments that could get to Pluto in the shortest amount of time.
He reminisces about both the January 2006 launch and the July 2015 flyby and presents two contrasting Pluto images, a pixellated image captured by the Hubble Space Telescope in 1994 and a detailed photo of Pluto taken by New Horizons just 16 hours before closest approach.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.