Black Holes Set the Clock for Life on Earth
Space Stories 2015
Every year, Discovery News turns to our faithful readers to see which space stories excited you the most and 2015 has been yet another incredible year for astronomy, spaceflight, planetary science and solar system discovery. After pulling together the nominations by considering web traffic over the past 12 months,the selection was put up for a vote
across social media and the top 10 quickly became obvious -- with a very clear winner. Can you guess which stories made it into the top 10? Read on to find out.
(Want to compare this year's top 10 with last year? Read "Top 10 Space Stories of 2014: Readers' Choice
With NASA's Dawn mission arriving at Ceres and New Horizons flying past Pluto, 2015 will forever be known as the "Year of the Dwarf Planet." But Ceres will forever be known as the dwarf planet we visited
. In March, the mission, that had made the slow transit from massive asteroid Vesta,arrived in Ceres orbit
, revealing a fascinating, pock-marked surface. A puzzle quickly presented itself -- what the heck are those bright spots? Although Dawn is orbiting the tiny world closer than ever,these bright patches still perplex scientists
, highlighting just what a mysterious and fascinating place Ceres is.PHOTOS: Ceres Delights: Dawn's Latest Dwarf Planet Views
20th Century Fox
Sure, it's a movie, but it's a movie that starred Matt Damon and co-starred SCIENCE! Not only did "The Martian" become a box office success, it was a rare movie that pleased scientists and the general public alike. There were afew scientific missteps
, but overall, it was a science fiction movie that realized that scientific accuracy can drive a great story forward without having to unnecessarily stray into scientific fantasy.
The Martian: Science vs. Fiction
Tour 'The Martian' Movie Set... On Mars
While many of the headlines focus on its younger roving cousin, Curiosity, NASA's Mars Exploration Rover Opportunity is still exploring the Red Planet despite 10 years of dusty wear and tear. The veteran robothas even completed an extraterrestrial marathon this year
, proving thatyears of steady progress
, despiterecently suffering more "amnesia" problems
, can pay off. Be sure to keep an eye on this mission, it's not done with Mars quite yet.MORE: 10 Years On Mars: Opportunity’s First Sols
The NASA/ESA Hubble Space Telescope is nothing short of a scientific and cultural phenomenon. Since 1990, the powerful space telescope has been pushing the boundaries of astronomical breakthroughs, refining our understanding of our place in the cosmos. And this year it celebrated its
quarter of a century
in space -- an incredible feat. As we look forward to the launch of NASA's James Webb Space Telescope (scheduled for 2018), we can only hope that Hubble's successor will have the longevity of the world's most famous space telescope.
Hubble at 25: The Space Telescope by the Numbers
Hubble at 25: What's Next for the Space Telescope?
Hubble at 25: Space Telescope's Top Science Discoveries
Hubble at 25: Brief History of the Hubble Space Telescope
continues to wow the world with incredible images and science from the slopes of Mount Sharp in the center of Gale Crater. The robotic geologist has not only revealed the stunning array of surface features the region has to offer, but it has also discovered potential for past habitable environments andan abundance of evidence for past liquid water flowing on Mars' surface
. It is a mission of epic proportions and has been a Reader's Choice favorite since it landed on the Red Planet in 2012 -- we can't wait to see what adventures Curiosity has in store for us in 2016.PHOTOS: Curiosity Plays in Sandy Martian Dunes
After a decade of orbiting Saturn, NASA's Cassini mission has startedits farewell tour
. Having most recently carried out its final flyby of enigmatic moon Enceladus, the spacecraft will begin maneuvers in 2016 that will ultimately see the mission fly through the planet's ring plane. Then, the spacecraftwill conclude its "Grand Finale"
, burning up in Saturn's atmosphere. 2015 has been a huge year for Cassini, revealing more incredible science about Saturn's system of moons, rings and dynamic atmosphere and we look forward to more science and beautiful images like this onebefore mission end
.MORE: Cassini's Final Flyby of Ice Moon Enceladus
This story rapidly became 2015's viral story of the year because...
Actually, it'sprobably a cloud of comets
, but the mere hint ofa possible alien megastructure orbiting a star some 1,500 light-years away
was enough to throw the internet into a spin. But the best thing about this story is that NASA's Kepler space telescope was thrown into the limelight and the stunning science of exoplanet detection became an international talking point. Since the original detection of the weird transit signal discovered by citizen scientists of the Planet Hunters project, the SETI Institute has turned its powerful Allen Telescope Array at Tabby's Starto find no transmitting aliens
. Still, it doesn't mean it's
aliens, it just means there are far more likely explanations.MORE: Has Kepler Discovered an Alien Megastructure?
Ahhh, water on Mars. Yes, we already know that there's water ICE on Mars, but this time it's different. Well, it MIGHT be different. Way back in 2011, some strange seasonal channels were spotted by NASA's Mars Reconnaissance Orbiter on Martian slopes. Though they looked like channels created by flows of liquid water, scientists urged caution -- Mars' atmosphere is so cold and thin, only short-lived water ice should exist, right? But after orbital analysis this year, the chemical residue of these channels was analyzed, revealing that these channels may well be causedby gushing liquid water
. However, this water isn't your fresh mountain spring variety --it's highly toxic water
laced with perchlorates,if it is indeed liquid water...
MORE: So Liquid Water Flows on Mars -- Now What?
Commercial access to space has been ramping-up in recent years and 2015 has seen some of the biggest advances.Orbital Sciences has bounced back
after itsAntares rocket explosion
in 2014 and, though suffering its own huge setback witha Falcon 9 rocket explosion
in June, SpaceX returned with adramatic launch and 1st stage rocket return this month
. Add these historic advances toBlue Origins own suborbital rocket return
and we have seen 12 exciting months of commercial spaceflight successes not only to resupply the space station, but also to launch satellites and refine rocket technology. Next stop Mars?Who knows
.MORE: Lesson of SpaceX Rocket Landing: Try, Try, Try Again
It's been a long wait, but in July, NASA's New Horizons mission flew through the Pluto-Charon system for itshistoric and long awaited flyby
. The spacecraft, which took nearly a decade to reach the outer solar system, is now blasting through the Kuiper Belt and mission scientists aresteering it toward a Kuiper Belt object (KBO)
for another flyby in 2019. But its Pluto flyby was just the beginning -- the spacecraft recorded so much data that it continues to beam back detailed information about the dwarf planet,its weirdly dynamic surface
, it'scrazy assortment of moons
and someperplexing mysteries along the way
. This has been a historic year; we're finally seeing Pluto up-close and in high-definition for the first time since it was discovered by American astronomer Clyde Tombaugh in 1930.PHOTOS: Dive Onto Pluto's High-Resolution Landscape
There is a chance -- just a chance -- that if black holes rule the universe, they could have "switched on" habitable planets, such as Earth, allowing them to support complex life.
It's an unavoidable implication of the work of astrophysicist Paul Mason, who is examining the role of the super high-energy particles from black holes and exploding stars in the advent of habitable planets.
Before life started on Earth, the planet was bathed in deadly radiation from the younger, angrier sun as well as a high tide of energetic particles -- a.k.a. cosmic rays -- being blasted around the galaxy and universe by exploding stars and giant black holes at the centers of galaxies. At some point the cosmic ray flux dropped enough so that life on Earth -- and on any Earth-like planet anywhere in the universe -- had a chance to flourish.
“It has taken the universe a while for the cosmic ray density and the frequency of bad events to decrease enough for life to handle it,” Mason told Discovery News. Mason is a professor at New Mexico State University in Las Cruces and presented his work on Wednesday at the meeting of the American Astronomical Society in Kissimmee, Fla.
Those bad events include supernovas -- the explosive deaths of very large and short-lived stars -- which were much more common in the early universe, when the rates of stars births was far higher, said Mason. Other very bad events were the storms of radiation that might have blown from the gigantic central black holes of galaxies when they gulped down matter. Such feeding frenzies -- and the harsh, sterilizing radiation they released -- were also more common in the past, as astronomers have learned by looking at more distant, and therefore more ancient, galaxies.
Compounding the early universe's problem with life is the fact that everything was much closer together. The small young universe was packed thick with sterilizing cosmic rays. It took billions of years for the expanding universe to pull things apart and help thin that deadly soup.
“It implies that the expansion of the universe is important for life,” Mason said, regarding this cosmic ray perspective on the universe.
Artist's impression of a spinning supermassive black hole with a surrounding accretion disk and relativistic jets.NASA/JPL-Caltech
What also helped life eventually fend off cosmic rays were the leftovers of all those supernovas. Dying stars are element factories which created the oxygen and nitrogen atoms that are now the primary components of our atmosphere. That atmosphere is what protects us from all but the most powerful cosmic rays that are still banging around the galaxy.
Mason's cosmic ray story seems to fit the observable universe, but there are still lots of unanswered questions. For instance, do all giant black holes necessarily zap their galaxies with the most dangerous, highest-energy cosmic rays?
“It's not very well established that these (giant black holes) release very high energy cosmic rays,” said physicist Dimitra Atri of the Blue Marble Space Institute of Science in Seattle.
And there is also the question of just what dose of cosmic rays is actually bad for life.
“If a (cosmic ray) dose is high enough it can kill something,” said Atri. “But at the same time it can cause mutations and lead to evolution of many more types of species.”
A lethal dose to a human is also not necessarily lethal to other organisms, Atri added. It's even conceivable that there are forms of life -- bacteria, for instance -- that thrive on cosmic rays and that we might find them within the Earth itself. If so, cosmic rays might not be such a key factor for habitability after all.
“There is a big spectrum for life on Earth,” said Atri. “If you look closely at habitability, it is more about water.”
As for Earth's chances of being one of the first living planets in the universe, “We don't know is that this means Earth is among the earliest,” said Mason. Right now, he said, it's a very interesting matter of speculation.