Dense Star Clusters Could be the Places Where Black Hole Mergers are Common

In February of 2016, scientists working for the Laser Interferometer Gravitational-Wave Observatory (LIGO) made history when they announced the first-ever detection of gravitational waves. Not only did this discovery confirm a century-old prediction made by Einstein’s Theory of General Relativity, it also confirmed the existence of stellar binary black holes – which merged to produce the signal in the first place.

And now, an international team led by MIT astrophysicist Carl Rodriguez has produced a study that suggests that  black holes may merge multiple times. According to their study, these “second-generation mergers” likely occur within globular clusters, the large and compact star clusters that typically orbit at the edges of galaxies – and which are densely-packed with hundreds of thousands to millions of stars.

The study, titled “Post-Newtonian Dynamics in Dense Star Clusters: Highly Eccentric, Highly Spinning, and Repeated Binary Black Hole Mergers“, recently appeared in the Physical Review Letters. The study was led by Carl Rodriguez, a Pappalardo fellow in MIT’s Department of Physics and the Kavli Institute for Astrophysics and Space Research, and included members from the Institute of Space Sciences and the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA).

As Carl Rodriguez explained in a recent MIT press release:

“We think these clusters formed with hundreds to thousands of black holes that rapidly sank down in the center. These kinds of clusters are essentially factories for black hole binaries, where you’ve got so many black holes hanging out in a small region of space that two black holes could merge and produce a more massive black hole. Then that new black hole can find another companion and merge again.”

Globular clusters have been a source of fascination ever since astronomers first observed them in the 17th century. These spherical collections of stars are among the oldest known stars in the Universe, and can be found in most galaxies. Depending on the size and type of galaxy they orbit, the number of clusters varies, with elliptical galaxies hosting tens of thousands while galaxies like the Milky Way have over 150.

For years, Rodriguez has been investigating the behavior of black holes within globular clusters to see if they interact with their stars differently from black holes that occupy less densely-populated regions in space. To test this hypothesis, Rodriguez and his colleagues used the Quest supercomputer at Northwestern University to conduct simulations on 24 stellar clusters.

These clusters ranged in size from 200,000 to 2 million stars and covered a range of different densities and metallic compositions. The simulations modeled the evolution of individual stars within these clusters over the course of 12 billion years. This span of time was enough to follow these stars as they interacted with each other, and eventually formed black holes.

In February 2016, LIGO detected gravity waves for the first time. As this artist's illustration depicts, the gravitational waves were created by merging black holes. The third detection just announced was also created when two black holes merged. Credit: LIGO/A. Simonnet.
Artist’s impression of merging binary black holes. Credit: LIGO/A. Simonnet.

The simulations also modeled the evolution and trajectories of black holes once they formed. As Rodriguez explained:

“The neat thing is, because black holes are the most massive objects in these clusters, they sink to the center, where you get a high enough density of black holes to form binaries. Binary black holes are basically like giant targets hanging out in the cluster, and as you throw other black holes or stars at them, they undergo these crazy chaotic encounters.”

Whereas previous simulations were based on Newton’s physics, the team decided to add Einstein’s relativistic effects into their simulations of globular clusters. This was due to the fact that gravitational waves were not predicted by Newton’s theories, but by Einstein’s Theory of General Relativity. As Rodriguez indicated, this allowed for them to see how gravitational waves played a role:

“What people had done in the past was to treat this as a purely Newtonian problem. Newton’s theory of gravity works in 99.9 percent of all cases. The few cases in which it doesn’t work might be when you have two black holes whizzing by each other very closely, which normally doesn’t happen in most galaxies… In Einstein’s theory of general relativity, where I can emit gravitational waves, then when one black hole passes near another, it can actually emit a tiny pulse of gravitational waves. This can subtract enough energy from the system that the two black holes actually become bound, and then they will rapidly merge.”

Artist’s conception shows two merging black holes similar to those detected by LIGO on January 4th, 2017. Credit: LIGO/Caltech

What they observed was that inside the stellar clusters, black holes merge with each other to create new black holes. In previous simulations, Newtonian gravity predicted that most binary black holes would be kicked out of the cluster before they could merge. But by taking relativistic effects into account, Rodriguez and his team found that nearly half of the binary black holes merged to form more massive ones.

As Rodriguez explained, the difference between those that merged and those that were kicked out came down to spin:

“If the two black holes are spinning when they merge, the black hole they create will emit gravitational waves in a single preferred direction, like a rocket, creating a new black hole that can shoot out as fast as 5,000 kilometers per second — so, insanely fast. It only takes a kick of maybe a few tens to a hundred kilometers per second to escape one of these clusters.”

This raised another interesting fact about previous simulations, where astronomers believed that the product of any black hole merger would be kicked out of the cluster since most black holes are assumed to be rapidly spinning. However, the gravity wave measurements recently obtained from LIGO appear to contradict this, which has only detected the mergers of binary black holes with low spins.

Artist’s impression of two merging black holes. Credit: Bohn, Throwe, Hébert, Henriksson, Bunandar, Taylor, Scheel/SXS

This assumption, however, seems to contradict the measurements from LIGO, which has so far only detected binary black holes with low spins. To test the implications of this, Rodriguez and his colleagues reduced the spin rates of the black holes in their simulations. What they found was that nearly 20% of the binary black holes from clusters had at least one black hole that ranged from being 50 to 130 solar masses.

Essentially, this indicated that these were “second generation” black holes, since scientists believe that this mass cannot be achieved by a black hole that formed from a single star. Looking ahead, Rodriguez and his team anticipate that if LIGO detects an object with a mass within this range, it is likely the result of black holes merging within dense stellar cluster, rather than from a single star.

“If we wait long enough, then eventually LIGO will see something that could only have come from these star clusters, because it would be bigger than anything you could get from a single star,” Rodriguez says. “My co-authors and I have a bet against a couple people studying binary star formation that within the first 100 LIGO detections, LIGO will detect something within this upper mass gap. I get a nice bottle of wine if that happens to be true.”

The detection of gravitational waves was a historic accomplishment, and one that has enabled astronomers to conduct new and exciting research. Already, scientists are gaining new insight into black holes by studying the byproduct of their mergers. In the coming years, we can expect to learn a great deal more thanks to improve methods and increased cooperation between observatories.

Further Reading: MIT, Physical Review Letters

Cold-War Era Derived ICBM Blasts Military ORS-5 Surveillance and Space Junk Tracking Satellite to Orbit: Gallery

ICBM derived Minotaur IV overnight launch of the ORS-5 space situational awareness and debris tracking satellite for the U.S. Air Force at 2:04 a.m. EDT on August 26, 2017 from Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

CAPE CANAVERAL AIR FORCE STATION, FL — A Cold War-era derived Peacekeeper ICBM missile formerly armed with multiple nuclear warheads and now modified as a payload orbiter successfully launched an urgently needed space situational awareness and space junk tracking satellite to equatorial orbit overnight this morning, Aug. 26, for the U.S. military from the Florida Space Coast.

Following a nearly 3 hour delay due to day long dismal weather causing locally heavy rain storms and lighting in central Florida, an Orbital ATK Minotaur IV rocket carrying the ORS-5 tracking satellite for the USAF finally lifted off in the wee hours Saturday morning, Aug. 26 at 2:04 a.m. EDT from Cape Canaveral Air Force Station in Florida.

The five stage solid fueled Minotaur IV roared rapidly off Space Launch Complex 46 (SLC-46) on a half million pounds of thrust and quickly disappeared into the clouds from the perspective of our nearby media launch viewing site on this inaugural launch of the rocket from the Cape.

Check back here to see the expanding gallery of launch photos and videos recorded by myself and space journalist colleagues!

Orbital ATK Minotaur IV rocket streaks to orbit after blastoff carrying the ORS-5 space situational awareness and debris tracking satellite to orbit for the military at 2:04 a.m. EDT on August 26, 2017 from pad 46 on Cape Canaveral Air Force Station in Florida. Credit: Julian Leek

The gap filling ORS-5 space surveillance satellite is a low cost mission technology demonstration mission that will track orbiting threats for the U.S. Air Force – and offered a thrilling nighttime launch experience to those who stayed awake and braved the post midnight time slot.

The converted ICBM motor ignition produced a flash of extremely bright light that briefly turned night into day. The maiden Minotaur from the Cape gushed intensely at liftoff and left a huge exhaust trailing in its wake as it accelerated to orbit.

Orbital ATK Minotaur IV rocket streaks to orbit after blastoff darting in and out of clouds to deliver the ORS-5 space situational awareness and debris tracking satellite to equatorial orbit for the U.S. Air Force at 2:04 a.m. EDT on August 26, 2017 from Cape Canaveral Air Force Station, FL – as seen from 5th Space Launch Squadron building roof on CCAFS. Credit: Ken Kremer/kenkremer.com

The ORS-5 is a single satellite constellation with a primary mission to provide space situational awareness of the geosynchronous orbit belt for Combatant Commanders’ urgent needs, according to Brig. Gen. Wayne Monteith, 45th Space Wing commander and mission Launch Decision Authority at Cape Canaveral Air Force Station

The ORS-5 mission, which stands for Operationally Responsive Space-5, marks the first launch of a Minotaur IV rocket from Cape Canaveral Air Force Station and the first use of SLC-46 since 1999.

SLC-46 is operated under license by Space Florida, which invested more than $6 million dollars of state funds into pad upgrades and renovations.

Orbital ATK Minotaur IV rocket streaks to orbit after blastoff carrying the ORS-5 space situational awareness and debris tracking satellite to orbit for the military at 2:04 a.m. EDT on August 26, 2017 from pad 46 on Cape Canaveral Air Force Station in Florida. Credit: Michael Seeley/WeReportSpace

The ORS-5 satellite built for the USAF Operationally Responsive Space Office will provide the US military with space-based surveillance and tracking of other satellites both friend and foe as well as space debris in geosynchronous orbit, 22,236 miles above the equator.

ORS-5 is like a telescope wrapped in a satellite that will aim up to seek threats from LEO to GEO using cameras and spectrometer sensors.

Also known as SensorSat, ORS-5 is designed to scan for other satellites and debris to aid the U.S. military’s tracking of objects in geosynchronous orbit for a minimum of three years and possibly longer if its on board sensor and spacecraft systems continue functioning in a useful and productive manner.

The Minotaur IV is a five stage rocket comprised of three stages of a decommissioned Cold War-era Peacekeeper Intercontinental Ballistic Missile (ICBM) that has been modified to add two additional Orbital ATK Orion 38 solid rocket motors for the upper stages.

Approximately 28 minutes after liftoff at 2:04 a.m. EDT, the Minotaur IV deployed the ORS-5 satellite into its targeted low inclination orbit 372 miles (599 kilometers) above the earth, Orbital ATK confirmed.

“From this orbit, ORS-5 will deliver timely, reliable and accurate space situational awareness information to the United States Strategic Command through the Joint Space Operations Center.”

Orbital ATK Minotaur IV rocket soars to orbit after blastoff darting artfully in and out of clouds to deliver the ORS-5 space situational awareness and debris tracking satellite to orbit for the U.S. Air Force at 2:04 a.m. EDT on August 26, 2017 from Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

“This was our first Minotaur launch from Cape Canaveral Air Force Station, demonstrating the rocket’s capability to launch from all four major U.S. spaceports,” said Rich Straka, Vice President and General Manager of Orbital ATK’s Launch Vehicles Division.

ICBM derived Minotaur IV overnight launch of the ORS-5 space situational awareness and debris tracking satellite for the U.S. Air Force at 2:04 a.m. EDT on August 26, 2017 from Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

This Minotaur IV rocket is a retired Cold War-era ICBM missile once armed with nuclear warheads aimed at the former Soviet Union that can now launch satellites for purposes other than offensive nuclear war retaliation.

So on the event of a nuclear first or retaliatory strike, this is how the world could potentially end in utter destruction and nuclear catastrophy.

To get an up-close feeling of the sounds and fury watch this Minotaur IV/ORS-5 launch video compilation from colleague Jeff Seibert from our media launch viewing site from the roof of the 5th Space Launch Squadron building on Cape Canaveral Air Force Station, FL.

Video Caption: Orbital ATK launch of Minotaur ORS 5 at 2:04 a.m. EDT on Aug. 26, 2017. None of the videos are sped up, it really takes off that fast. The solid fuel Peacekeeper missile segments were repurposed to launch the ORS-5 satellite from Launch Complex 46 on CCAFS., Fl. Credit: Jeff Seibert

Overall the ORS-5 launch was the 26th blastoff in Orbital ATK’s Minotaur family of launch vehicles which enjoy a 100% success rate to date.

Today’s launch was the 6th for the Minotaur IV version.

“With a perfect track record of 26 successful launches, the Minotaur family has proven to be a valuable and reliable asset for the Department of Defense,” said Straka.

“Orbital ATK has launched nearly 100 space launch and strategic rockets for the U.S. Air Force,” said Scott Lehr, President of Orbital ATK’s Flight Systems Group. “We’re proud to be a partner they can count on.”

Orbital ATK Minotaur IV rocket streaks to orbit through low hanging clouds that instantly become brightly illuminated as the booster engines flames pass through, while leaving towering exhaust plume in its wake. The mission carried the ORS-5 satellite tracker to equatorial orbit for the U.S. Air Force at 2:04 a.m. EDT on August 26, 2017 from Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com

The past two weeks have been a super busy time at the Kennedy Space Center and Cape Canaveral. This morning’s post midnight launch was the third in just 11 days – and the second in a week!

A ULA Atlas V launched the NASA TDRS-M science relay satellite last Friday, Aug 18. And a SpaceX Falcon 9 launched the Dragon CRS-12 cargo resupply mission to the International Space Station (ISS) on Monday, Aug. 14.

“The ORS-5 Minotaur IV launch was the true epitome of partnership,” Gen. Monteith said.

“A collaborative effort between multiple mission partners, each group came together flawlessly to revolutionize how we work together on the Eastern Range. Teamwork is pivotal to making us the ‘World’s Premier Gateway to Space’ and I couldn’t be prouder to lead a Wing that not only has launched over a quarter of the world’s launches this year, but also three successful, launches from three different providers, in less than two weeks.”

ORS-5 was designed and built by Massachusetts Institute of Technology’s Lincoln Laboratory facility in Lexington, Massachusetts at a cost of $49 million.


The ORS-5 or SensorSat satellite will provide the US military with space-based surveillance and tracking of other satellites both friend and foe and space debris in geosynchronous orbit 22,236 miles above the equator. Credit: MIT Lincoln Laboratory

In July 2015 the U.S. Air Force’s Operationally Responsive Space (ORS) Office awarded Orbital ATK a $23.6 million contract to launch the ORS-5 SensorSat on the Minotaur IV launch vehicle.

ORS-5/SensorSat was processed for launch and encapsulation inside the 2.3 meter diameter payload fairing at Astrotech Space Operations processing facility in Titusville, Florida.

Orbital ATK Minotaur IV rocket streaks to orbit after blastoff darting in and out of clouds to deliver the ORS-5 space situational awareness and debris tracking satellite to equatorial orbit for the U.S. Air Force at 2:04 a.m. EDT on August 26, 2017 from Cape Canaveral Air Force Station, FL – as seen from 5th Space Launch Squadron building roof on CCAFS. Credit: Ken Kremer/kenkremer.com
Orbital ATK Minotaur IV rocket streaks to orbit after blastoff darting in and out of clouds to deliver the ORS-5 space situational awareness and debris tracking satellite to equatorial orbit for the U.S. Air Force at 2:04 a.m. EDT on August 26, 2017 from Cape Canaveral Air Force Station, FL – as seen from 5th Space Launch Squadron building roof on CCAFS. Credit: Ken Kremer/kenkremer.com

Watch for Ken’s continuing onsite Minotaur IV ORS-5, TDRS-M, CRS-12, and NASA and space mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

Orbital ATK Minotaur IV rocket streaks to orbit through low hanging clouds that instantly illuminate as the booster engines flames pass through. This first Minotaur launch from the Cape carried the ORS-5 satellite tracker to equatorial orbit for the U.S. Air Force at 2:04 a.m. EDT on August 26, 2017 from Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
Orbital ATK Minotaur IV rocket description. Credit: Orbital ATK/USAF
Minotaur IV ORS-5 mission patch

Threat Tracking USAF Satellite Launching Nighttime Aug 25 on Cape Debut of Retired ICBM Minotaur Rocket: Watch Live

An Orbital ATK Minotaur IV rocket carrying the ORS-5 USAF surveillance satellite is slated for its maiden liftoff from Cape Canaveral Air Station, Florida at 11:15 p.m. EDT on August 25, 2017 on a retired ICBM. Credit: U.S. Air Force/Patrick AFB

CAPE CANAVERAL AIR FORCE STATION, FL — A gap filling space surveillance satellite that will track orbiting threats for the U.S. Air Force is set for an thrilling nighttime blastoff Friday, Aug. 25 on the maiden mission of the Minotaur IV rocket from Cape Canaveral that’s powered by a retired Cold War-era ICBM missile – once armed with nuclear warheads.

The ORS-5 satellite will provide the US military with space-based surveillance and tracking of other satellites both friend and foe as well as space debris in geosynchronous orbit, 22,236 miles above the equator.

The Orbital ATK Minotaur IV rocket carrying the ORS-5 tracking satellite for the USAF Operationally Responsive Space Office is targeting liftoff just before midnight Friday at 11:15 p.m. EDT from Space Launch Complex-46 (SLC-46) at Cape Canaveral Air Force Station.

“We are go for launch of Orbital ATK’s Minotaur IV rocket Friday night,” Orbital ATK confirmed.

The ORS-5 mission, which stands for Operationally Responsive Space-5, marks the first launch of a Minotaur IV rocket from Cape Canaveral and the first use of SLC-46 since 1999.

The Minotaur IV is a five stage rocket comprised of three stages of a decommissioned Cold War-era Peacekeeper Intercontinental Ballistic Missile (ICBM) that has been modified to add two additional Orbital ATK Orion 38 solid rocket motors for the upper stages.

Being a night launch and the first of its kind will surely make for a spectacular sky show.

Plus if you want to see how the world could potentially end in nuclear catastrophy, come watch the near midnight launch of the Orbital ATK Minotaur IV rocket that’s a retired Peacekeeper ICBM once armed with nuclear warheads aimed at the Russians but now carrying the USAF ORS-5 surveillance satellite instead.

Its well worth your time if you can watch the Minotaur launch with your own eyeballs. It can be easily viewed from numerous local area beaches, parks, restaurants and more.

Minotaur IV rocket stands at pad 46 with the USAF ORS-5 surveillance satellite for its first launch from Cape Canaveral Air Station, Florida on August 25, 2017. Credit: Orbital ATK

Furthermore, its been in a super busy time at the Kennedy Space Center and Cape Canaveral. Because, if all goes well Friday’s midnight launch will be the third in just 11 days – and the second in a week!

A ULA Atlas V launched the NASA TDRS-M science relay satellite last Friday, Aug 18. And a SpaceX Falcon 9 launched the Dragon CRS-12 cargo resupply mission to the International Space Station (ISS) on Monday, Aug. 14.

You can watch the launch live via the Orbital ATK website here: www.orbitalatk.com

The live Orbital ATK broadcast will begin approximately 20 minutes before the launch window opens.

The webcast will be hosted by former CNN space reporter John Zarrella.

The launch window opens at 11:15 p.m. EDT August 25. It extends for four hours until 3:15 a.m. EDT August 26.

In the event of delay for any reason, the next launch opportunity is Saturday, Aug. 26. The launch window remains the same from 11:15 p.m. EDT August 26 to 3:15 a.m. EDT August 27.

The weather looks somewhat iffy at this time with only a 60% chance of favorable conditions at launch time according to U.S. Air Force meteorologists with the 45th Space Wing Weather Squadron at Patrick Air Force Base. The primary concerns on Aug. 25 are for thick clouds and cumulus clouds.

The weather odds deteriorate to only 40% favorable for the 24 hour scrub turnaround day on Aug. 26. The primary concerns on Aug. 26 are for thick clouds, cumulus clouds and lightning.


The ORS-5 or SensorSat satellite will provide the US military with space-based surveillance and tracking of other satellites both friend and foe and space debris in geosynchronous orbit 22,236 miles above the equator. Credit: MIT Lincoln Laboratory

ORS-5 is like a telescope wrapped in a satellite that will aim up to seek threats from LEO to GEO.

ORS-5, also known as SensorSat, is designed to scan for other satellites and debris to aid the U.S. military’s tracking of objects in geosynchronous orbit for a minimum of three years and possibly longer if its on boards sensor and satellite systems continue functioning in a useful and productive manner.

“The delivery and upcoming launch of ORS-5 marks a significant milestone in fulfilling our commitment to the space situational awareness mission and U.S. Strategic Command,” said Lt. Gen. John F. Thompson, commander of the Space and Missile Systems Center and Air Force program executive officer for Space. “It’s an important asset for the warfighter and will be employed for at least three years.”

The ORS-5 satellite has a payload mass of 140 kg. It will be launched into a low inclination equatorial orbit of 600 km x 600 km (373 mi x 373 mi) at zero degrees.

“This will be the largest low-Earth orbit inclination plane change in history – 28.5 degrees latitude to equatorial orbit,” says Orbital ATK.

“The Minotaur IV 4th stage will put ORS-5 into initial orbit & the payload insertion stage will make a hard left to get to equatorial orbit.”

The Cape Canaveral AFB launch site for this Minotaur IV was chosen, rather than NASA’s Wallops Flight Facility in Virginia based on the final orbit required for ORS-5, Orbital ATK told Universe Today at a prelaunch media briefing.

The Minotaur IV is not powerful enough to deliver ORS-5 to the desired orbit from Wallops.

ORS-5 was designed and built by Massachusetts Institute of Technology’s Lincoln Laboratory facility in Lexington, Massachusetts at a cost of $49 million.

In July 2015 the U.S. Air Force’s Operationally Responsive Space (ORS) Office awarded Orbital ATK a $23.6 million contract to launch the ORS-5 SensorSat on the Minotaur IV launch vehicle.

ORS-5/SensorSat was processed for launch and encapsulation inside the 2.3 meter diameter payload fairing at Astrotech Space Operations processing facility in Titusville, Florida.

The Minotaur IV is quite similar to Orbital ATK’s Minotaur V launch vehicle which successfully propelled NASA’s LADEE lunar orbiter to the Moon for NASA during a night launch from the agency’s Wallops Flight Facility in Virginia in Sept. 2013.

Launch of NASA’s LADEE lunar orbiter on Friday night Sept. 6, 2013 at 11:27 p.m. EDT on the maiden flight of the Minotaur V rocket from NASA Wallops, Virginia. Credit: Ken Kremer/kenkremer.com

The Minotaur V also utilizes the first three stages of the decommissioned Peacekeeper ICBM missile.

Overall the ORS-5 launch will be the 26th blastoff in Orbital ATK’s Minotaur family of launch vehicles which enjoy a 100% success rate to date.

Gantry doors open to expose Minotaur V rocket launching LADEE lunar orbiter to the Moon on Sept 6, 2013 from Launch Pad 0B at NASA Wallops Island. Credit: Ken Kremer/kenkremer.com

The U.S. Air Force has a stockpile of about 180 surplus Peacekeeper motors, but not all are launch capable, the USAF told Universe Today at a prelaunch media briefing.

The USAF furnishes the Peacekeeper motors to Orbital ATK after first refurbishing the booster stages at Vandenberg AFB, Ca.

Orbital ATK then upgrades the stages by adding their own “flight-proven avionics, structures, software and other components that are common among Orbital ATK’s space launch vehicles” and integrating the firms Orion 38 solid rocket motors for the two upper stages.

“A combined government and contractor team of mission partners executed final ground activities including a Launch Base Compatibility Test to verify satellite integrity after shipment, an intersegment test to verify communication compatibility from the satellite to the on-orbit operations center and the final battery reconditioning for launch, prior to its integration with the Minotaur IV launch vehicle,” says the USAF.

Watch for Ken’s continuing onsite Minotaur IV ORS-5, TDRS-M, CRS-12, and NASA and space mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

Minotaur IV ORS-5 Mission Trajectory. Credit: Orbital ATK

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Learn more about the 2017 Total Solar Eclipse, upcoming Minotaur IV ORS-5 military launch on Aug. 25, recent ULA Atlas TDRS-M NASA comsat on Aug. 18, 2017 , SpaceX Dragon CRS-12 resupply launch to ISS on Aug. 14, NASA missions and more at Ken’s upcoming outreach events at Kennedy Space Center Quality Inn, Titusville, FL:

Aug 25-26: “2017 Total Solar Eclipse, Minotaur IV ORS-5, TDRS-M NASA comsat, SpaceX CRS-12 resupply launches to the ISS, Intelsat35e, BulgariaSat 1 and NRO Spysat, SLS, Orion, Commercial crew capsules from Boeing and SpaceX , Heroes and Legends at KSCVC, ULA Atlas/John Glenn Cygnus launch to ISS, SBIRS GEO 3 launch, GOES-R weather satellite launch, OSIRIS-Rex, Juno at Jupiter, InSight Mars lander, SpaceX and Orbital ATK cargo missions to the ISS, ULA Delta 4 Heavy spy satellite, Curiosity and Opportunity explore Mars, Pluto and more,” Kennedy Space Center Quality Inn, Titusville, FL, evenings

Stacking the 4th stage of the Orbital ATK Minotaur IV rocket in preparation for the August 25, 2017 ORS-5 launch from Space Launch Complex 46, Cape Canaveral Air Station, Florida. Credit: Orbital ATK
Orbital ATK Minotaur IV rocket description. Credit: Orbital ATK/USAF
Minotaur IV ORS-5 mission patch

New Study Says Moon’s Magnetic Field Existed 1 Billion Years Longer Than We Thought

When it comes to the study of planets, moons, and stars, magnetic fields are kind of a big deal. Believed to be the result of convection in a planet, these fields can be the difference between a planet giving rise to life or becoming a lifeless ball of rock. For some time, scientists have known that has a Earth’s magnetic field, which is powered by a dynamo effect created by convection in its liquid, outer core.

Scientists have also long held that the Moon once had a magnetic field, which was also powered by convection in its core. Previously, it was believed that this field disappeared roughly 1 billion years after the Moon formed (ca. 3 to 3.5 billion years ago). But according to a new study from the Massachusetts Institute of Technology (MIT), it now appears that the Moon’s magnetic field continued to exist for another billion years.

The study, titled “A two-billion-year history for the lunar dynamo“, recently appeared in the journal Science Advances. Led by Dr. Sonia Tikoo, an Assistant Professor at Rutger’s University and a former researcher at MIT, the team analyzed ancient lunar rocks collected by NASA’s Apollo 15 mission. What they found was that the rock showed signs of a being in magnetic field when it was formed between 1 and 2.5 billion years ago.

Artist’s concept of a collision between proto-Earth and Theia, which led to the formation of Moon, ca. 4.5 billion years ago. Credit: NASA

The age of this rock sample means that it is significantly younger than others returned by the Apollo missions. Using a technique they developed, the team examined the sample’s glassy composition with a magnometer to determine its magnetic properties. They then exposed the sample to a lab-generated magnetic field and other conditions that were similar to those that existed on the Moon when the rock would have formed.

This was done by placing the rocks into a specially-designed oxygen-deprived oven, which was built with the help of Clement Suavet and Timothy Grove – two researchers from MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS) and co-authors on the study. The team then exposed the rocks to a tenuous, oxygen-free environment and heated them to extreme temperatures.

As Benjamin Weiss – a professor of planetary sciences at EAPS – explained:

“You see how magnetized it gets from getting heated in that known magnetic field, then you compare that field to the natural magnetic field you measured beforehand, and from that you can figure out what the ancient field strength was… In this way, we finally have gotten an accurate measurement of the lunar field.”

From this, they determined the lunar rock became magnetized in a field with a strength of about 5 microtesla. That’s many times weaker than Earth’s magnetic field when measured from the surface (25 – 65 microteslas), and two orders of magnitude weaker than what it was 3 to 4 billion years ago. These findings were quite significant, since they may help to resolve an enduring mystery about the Moon.

Cutaway of the Moon, showing its differentiated interior. Credit: NASA/SSERVI

Previously, scientists suspected that the Moon’s magnetic field died out 1.5 billion years after the Moon formed (ca. 3 billion years ago). However, they were unsure if this process happened rapidly, or if the Moon’s magnetic field endured, but in a weakened state. The results of this study indicate that the magnetic field did in fact linger for an additional billion years, dissipating about 2.5 billion years ago.

As Weiss indicated, this study raises new questions about the Moon’s geological history:

“The concept of a planetary magnetic field produced by moving liquid metal is an idea that is really only a few decades old. What powers this motion on Earth and other bodies, particularly on the moon, is not well-understood. We can figure this out by knowing the lifetime of the lunar dynamo.”

In other words, this new timeline of the Moon casts some doubt on the theory that a lunar dynamo alone is what powered its magnetic field in the past. Basically, it is now seen as a distinct possibility that the Moon’s magnetic field was powered by two mechanisms. Whereas one allowed for a dynamo in the core that powered its magnetic field for a good billion years after the Moon’s formation, a second one kept it going afterwards.

In the past, scientists have proposed that the Moon’s dynamo was powered by Earth’s gravitational pull, which would have caused tidal flexing in the Moon’s interior (much in the same way that Jupiter and Saturn’s powerful gravity drives geological activity in their moons interiors). In addition, the Moon once orbited much closer to Earth, which may have been enough to power its once-stronger magnetic field.

Artist's impression of a Mars-sized object crashing into the Earth, starting the process that eventually created our Moon. Credit: Joe Tucciarone
Artist’s impression of a Mars-sized object crashing into the Earth, starting the process that eventually created our Moon. Credit: Joe Tucciarone

However, the Moon gradually moved away from Earth, eventually reaching its current orbit about 3 billion years ago. This coincides with the timeline of the Moon’s magnetic field, which began to dissipate at about the same time. This could mean that by about 3 billion years ago, without the gravitational pull of the Earth, the core slowly cooled. One billion years later, the core had solidified to the point that it arrested the Moon;s magnetic field. As Weiss explained:

“As the moon cools, its core acts like a lava lamp – low-density stuff rises because it’s hot or because its composition is different from that of the surrounding fluid. That’s how we think the Earth’s dynamo works, and that’s what we suggest the late lunar dynamo was doing as well… Today the moon’s field is essentially zero. And we now know it turned off somewhere between the formation of this rock and today.”

These findings were made possible thanks in part by the availability of younger lunar rocks. In the future, the researchers are planning on analyzing even younger samples to precisely determine where the Moon’s dynamo died out completely. This will not only serve to validate the findings of this study, but could also lead to a more comprehensive timeline of the Moon’s geological history.

The results of these and other studies that seek to understand how the Moon formed and changed over time will also go a long way towards improving our understanding of how Earth, the Solar System, and extra-solar systems came to be.

Further Reading: Science Advances, MIT News

The 2016 Nobel Prize In Physics: It’s Complicated

Update: This year’s Nobel Prize in Physics has been awarded to David J. Thouless (University of Washington), F. Duncan M. Haldane (Princeton University), and J. Michael Kosterlitz of Brown University for “theoretical discoveries of topological phase transitions and topological phases of matter”. One half of the prize was awarded to Thouless while the other half was jointly awarded to Haldane and Kosterlitz.

The Nobel Prize in physics is a coveted award. Every year, the prize is bestowed upon the individual who is deemed to have made the greatest contribution to the field of physics during the preceding year. And this year, the groundbreaking discovery of gravitational waves is anticipated to be the main focus.

This discovery, which was announced on February 11th, 2016, was made possible thanks to the development of the Laser Interferometer Gravitational-Wave Observatory (LIGO). As such, it is expected that the three scientists that are most responsible for the invention of the technology will receive the Nobel Prize for their work. However, there are those in the scientific community who feel that another scientist – Barry Barish – should also be recognized.

But first, some background is needed to help put all this into perspective. For starers, gravitational waves are ripples in the curvature of spacetime that are generated by certain gravitational interactions and which propagate at the speed of light. The existence of such waves has been postulated since the late 19th century.

LIGO's two facilities, located in . Credit: ligo.caltech.edu
LIGO’s two observatories, the located in Livingston, Louisiana; and Hanford, Washington. Credit: ligo.caltech.edu

However, it was not until the late 20th century, thanks in large part to Einstein and his theory of General Relativity, that gravitational-wave research began to emerge as a branch of astronomy. Since the 1960s, various gravitational-wave detectors have been built, which includes the LIGO observatory.

Founded as a Caltech/MIT project, LIGO was officially approved by the National Science Board (NSF) in 1984. A decade later, construction began on the facility’s two locations – in Hanford, Washington and Livingston, Louisiana. By 2002, it began to obtain data, and work began on improving its original detectors in 2008 (known as the Advanced LIGO Project).

The credit for the creation of LIGO goes to three scientists, which includes Rainer Weiss, a professor of physics emeritus at the Massachusetts Institute of Technology (MIT); Ronald Drever, an experimental physics who was professor emeritus at the California Institute of Technology and a professor at Glasgow University; and Kip Thorne, the Feynman Professor of Theoretical Physics at Caltech.

In 1967 and 68, Weiss and Thorne initiated efforts to construct prototype detectors, and produced theoretical work to prove that gravitational waves could be successfully analyzed. By the 1970s, using different methods, Weiss and Denver both succeeded in building detectors. In the coming years, all three men remained pivotal and influential, helping to make gravitational astronomy a legitimate field of research.

 A bird's eye view of LIGO Hanford's laser and vacuum equipment area (LVEA). The LVEA houses the pre-stabilized laser, beam splitter, input test masses, and other equipment. Credit: ligo.caltech.edu
LIGO Hanford’s laser and vacuum equipment area (LVEA), which houses the pre-stabilized laser, beam splitter, input test masses, and other equipment. Credit: ligo.caltech.edu

However, it has been argued that without Barish – a particle physicist at Caltech – the discovery would never have been made. Having become the Principal Investigator of LIGO in 1994, he inherited the project at a very crucial time. It had begun funding a decade prior, but coordinating the work of Wiess, Thorne and Drever (from MIT, Caltech and the University of Glasgow, respectively) proved difficult.

As such, it was decided that a single director was needed. Between 1987 and 1994, Rochus Vogt – a professor emeritus of Physics at Caltech – was appointed by the NSF to fill this role. While Vogt brought the initial team together and helped to get the construction of the project approved, he proved difficult when it came to dealing with bureaucracy and documenting his researchers progress.

As such, between 1989 through 1994, LIGO failed to progress technically and organizationally, and had trouble acquiring funding as well. By 1994, Caltech eased Vogt out of his position and appointed Barish to the position of director. Barish got to work quickly, making significant changes to the way LIGO was administered, expanding the research team, and developing a detailed work plan for the NSF.

Barish was also responsible for expanding LIGO beyond its Caltech and MIT constraints. This he did through the creation of the independent LIGO Scientific Collaboration (LSC), which gave access to outside researchers and institutions. This was instrumental in creating crucial partnerships, which included the UK Science and Technology Facilities Council, the Max Planck Society of Germany, and the Australian Research Council.

Artist's impression of how massive bodies (like our Sun) distort space time. Credit: T. Pyle/Caltech/MIT/LIGO Lab
Artist’s impression of how massive bodies (like our Sun) distort space time. Such bodies also create gravity waves when they accelerate through space and time. Credit: T. Pyle/Caltech/MIT/LIGO Lab

By 1999, construction had wrapped up on the LIGO observatories, and by 2002, they began taking their first bits of data. By 2004, the funding and groundwork was laid for the next phase of LIGO development, which involved a multi-year shut-down while the detectors were replaced with improved “Advanced LIGO” versions.

All of this was made possible by Barish, who retired in 2005 to head up other projects. Thanks to his sweeping reforms, LIGO got to work after an abortive start, began to produce data, procured funding, crucial partnerships, and now has more than 1000 collaborators worldwide, thanks to the LSC program he established.

Little wonder then why some scientists think the Nobel Prize should be split four-ways, awarding the three scientists who conceived of LIGO and the one scientist who made it happen. And as Barish himself was quoted as saying by Science:

“I think there’s a bit of truth that LIGO wouldn’t be here if I didn’t do it, so I don’t think I’m undeserving. If they wait a year and give it to these three guys, at least I’ll feel that they thought about it,” he says. “If they decide [to give it to them] this October, I’ll have more bad feelings because they won’t have done their homework.”

The approximate locations of the two gravitational-wave events detected so far by LIGO are shown on this sky map of the southern hemisphere. . Credit: LIGO/Axel Mellinger
The approximate locations of the two gravitational-wave events detected so far by LIGO are shown on this sky map of the southern hemisphere. . Credit: LIGO/Axel Mellinger

However, there is good reason to believe that the award will ultimately be split three ways, leaving Barish out. For instance, Weiss, Drever, and Thorne have been honored three times already this year for their work on LIGO. This has included the Special Breakthrough Prize in Fundamental Physics, the Gruber Cosmology Prize, and Kavli Prize in Astrophysics.

What’s more, in the past, the Nobel Prize in physics has tended to be awarded to those responsible for the intellectual contributions leading to a major breakthrough, rather than to those who did the leg work. Out of the last six Prizes issued (between 2010 and 2015), five have been awarded for the development of experimental methods, observational studies, and theoretical discoveries.

Only one award was given for a technical development. This was the case in 2014 where the award was given jointly to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for “the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources”.

Basically, the Nobel Prize is a complicated matter. Every year, it is awarded to those who made a considerable contribution to science, or were responsible for a major breakthrough. But contributions and breakthroughs are perhaps a bit relative. Whom we choose to honor, and for what, can also be seen as an indication of what is valued most in the scientific community.

In the end, this year’s award may serve to highlight how significant contributions do not just entail the development of new ideas and methods, but also in bringing them to fruition.

Further Reading: Science, LIGO, Nobelprize.org

Musk Says Hyperloop Could Work On Mars… Maybe Even Better!

Elon Musk has always been up-front about his desire to see humans settle on the Red Planet. In the past few years, he has said that one of his main reasons for establishing SpaceX was to see humanity colonize Mars. He has also stated that he believes that using Mars as a “backup location” for humanity might be necessary for our survival, and even suggested we use nukes to terraform it.

And in his latest speech extolling the virtues of colonizing Mars, Musk listed another reason. The Hyperloop – his concept for a high-speed train that relies steel tubes, aluminum cars and maglev technology to go really fast – might actually work better in a Martian environment. The announcement came as part of the award ceremony for the Hyperloop Pod Competition, which saw 100 university teams compete to create a design for a Hyperloop podcar.

It was the first time that Musk has addressed the issue of transportation on Mars. In the past, he has spoken about establishing a colony with 80,000 people, and has also discussed his plans to build a Mars Colonial Transporter to transport 100 metric tons (220,462 lbs) of cargo or 100 people to the surface of Mars at a time (for a fee of $50,000 apiece). He has also discussed communications, saying that he would like to bring the internet to Mars once a colony was established.

Artist's concept of what a Hyperloop pod car might look like. Credit: Tesla
Artist’s concept of what a Hyperloop pod car’s interior might look like. Credit: Tesla

But in addressing transportation, Musk was able to incorporate another important concept that he has come up with, and which is also currently in development. Here on Earth, the Hyperloop would rely on low-pressure steel tubes and a series of aluminum pod cars to whisk passengers between major cities at speeds of up to 1280 km/h (800 mph). But on Mars, according to Musk, you wouldn’t even need tubes.

As Musk said during the course of the ceremony: “On Mars you basically just need a track. You might be able to just have a road, honestly. [It would] go pretty fast… It would obviously have to be electric because there’s no oxygen. You have to have really fast electric cars or trains or things.”

Essentially, Musk was referring to the fact that since Mars has only 1% the air pressure of Earth, air resistance would not be a factor. Whereas his high-speed train concept requires tubes with very low air pressure to reach the speed of sound here on Earth, on Mars they could reach those speeds out in the open. One might say, it actually makes more sense to build this train on Mars rather than on Earth!

The Hyperloop Pod Competition, which was hosted by SpaceX, took place between Jan 27th and 29th. The winning entry came from MIT, who’s design was selected from 100 different entries. Their pod car, which is roughly 2.5 meters long and 1 meter wide (8.2 by 3.2 feet), would weight 250 kg (551 lbs) and be able to achieve an estimated cruise speed of 110 m/s (396 km/h; 246 mph). While this is slightly less than a third of the speed called for in Musk’s original proposal, this figure representing cruising speed (not maximum speed), and is certainly a step in that direction.

Team MIT's Hyperloop pod car design. Credit: MIT/Twitter
Team MIT’s Hyperloop pod car design. Credit: MIT/Twitter

And while Musk’s original idea proposed that the pod be lifted off the ground using air bearings, the MIT team’s design called for the use of electrodynamic suspension to keep itself off the ground. The reason for this, they claimed, is because it is “massively simpler and more scalable.” In addition, compared to the other designs’ levitation systems, theirs had one of the lowest drag coefficients.

The team – which consists of 25 students with backgrounds in aeronautics, mechanical engineering, electrical engineering, and business management – will spend the next five months building and testing their pod. The final prototype will participate in a trial run this June, where it will run on the one-mile Hyperloop Test Track at SpaceX’s headquarters in California.

Since he first unveiled it back in 2013, Musk’s Hyperloop concept has been the subject of considerable interest and skepticism. However, in the past few years, two companies – Hyperloop Transportation Technologies (HTT) and Hyperloop Technologies – have emerged with the intention of seeing the concept through to fruition. Both of these companies have secured lucrative partnerships since their inception, and are even breaking ground on their own test tracks in California and Nevada.

And with a design for a podcar now secured, and tests schedules to take place this summer, the dream of a “fifth mode of transportation” is one step closer to becoming a reality! The only question is, which will come first – Hyperloops connecting major cities here on Earth, or running passengers and freight between domed settlements on Mars?

Only time will tell! And be sure to check out Team MIT’s video:

Further Reading: SpaceXhyperloop.it.edu

Exoplanet-Hunting TESS Satellite to be Launched by SpaceX

A conceptual image of the Transiting Exoplanet Survey Satellite. Image Credit: MIT

The search for exoplanets is heating up, thanks to the deployment of space telescopes like Kepler and the development of new observation methods. In fact, over 1800 exoplanets have been discovered since the 1980s, with 850 discovered just last year. That’s quite the rate of progress, and Earth’s scientists have no intention of slowing down!

Hot on the heels of the Kepler mission and the ESA’s deployment of the Gaia space observatory last year, NASA is getting ready to launch TESS (the Transiting Exoplanet Survey Satellite). And to provide the launch services, NASA has turned to one of its favorite commercial space service providers – SpaceX.

The launch will take place in August 2017 from the Cape Canaveral Air Force Station in Florida, where it will be placed aboard a Falcon 9 v1.1 – a heavier version of the v 1.0 developed in 2013. Although NASA has contracted SpaceX to perform multiple cargo deliveries to the International Space Station, this will be only the second time that SpaceX has assisted the agency with the launch of a science satellite.

This past September, NASA also signed a lucrative contract with SpaceX worth $2.6 billion to fly astronauts and cargo to the International Space Station. As part of the Commercial Crew Program, SpaceX’s Falcon 9 and Dragon spacecraft were selected by NASA to help restore indigenous launch capability to the US.

James Webb Space Telescope. Image credit: NASA/JPL
Artist’s impression of the James Webb Space Telescope, the space observatory scheduled for launch in 2018. Image Credit: NASA/JPL

The total cost for TESS is estimated at approximately $87 million, which will include launch services, payload integration, and tracking and maintenance of the spacecraft throughout the course of its three year mission.

As for the mission itself, that has been the focus of attention for many years. Since it was deployed in 2009, the Kepler spacecraft has yielded more and more data on distant planets, many of which are Earth-like and potentially habitable. But in 2013, two of four reaction wheels on Kepler failed and the telescope has lost its ability to precisely point toward stars. Even though it is now doing a modified mission to hunt for exoplanets, NASA and exoplanet enthusiasts have been excited by the prospect of sending up another exoplanet hunter, one which is even more ideally suited to the task.

Once deployed, TESS will spend the next three years scanning the nearest and brightest stars in our galaxy, looking for possible signs of transiting exoplanets. This will involve scanning nearby stars for what is known as a “light curve”, a phenomenon where the visual brightness of a star drops slightly due to the passage of a planet between the star and its observer.

By measuring the rate at which the star dims, scientists are able to estimate the size of the planet passing in front of it. Combined with measurements the star’s radial velocity, they are also able to determine the density and physical structure of the planet. Though it has some drawbacks, such as the fact that stars rarely pass directly in front of their host stars, it remains the most effective means of observing exoplanets to date.

Number of extrasolar planet discoveries per year through September 2014, with colors indicating method of detection:   radial velocity   transit   timing   direct imaging   microlensing. Image Credit: Public domain
Number of extrasolar planet discoveries on up to Sept. 2014, with colors indicating method of detection. Blue: radial velocity; Green: transit; Yellow: timing, Red: direct imaging; Orange: microlensing. Image Credit: Alderon/Wikimedia Commons

In fact, as of 2014, this method became the most widely used for determining the presence of exoplanets beyond our Solar System. Compared to other methods – such as measuring a star’s radial velocity, direct imaging, the timing method, and microlensing – more planets have been detected using the transit method than all the other methods combined.

In addition to being able to spot planets by the comparatively simple method of measuring their light curve, the transit method also makes it possible to study the atmosphere of a transiting planet. Combined with the technique of measuring the parent star’s radial velocity, scientists are also able to measure a planet’s mass, density, and physical characteristics.

With TESS, it will be possible to study the mass, size, density and orbit of exoplanets. In the course of its three-year mission, TESS will be looking specifically for Earth-like and super-Earth candidates that exist within their parent star’s habitable zone.

This information will then be passed on to Earth-based telescopes and the James Webb Space Telescope – which will be launched in 2018 by NASA with assistance from the European and Canadian Space Agencies – for detailed characterization.

The TESS Mission is led by the Massachusetts Institute of Technology – who developed it with seed funding from Google – and is overseen by the Explorers Program at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Further Reading: NASA, SpaceX

 

Earth May Have Lost Some Primoridial Atmosphere to Meteors

Earth's Hadean Eon is a bit of a mystery to us, because geologic evidence from that time is scarce. Researchers at the Australian National University have used tiny zircon grains to get a better picture of early Earth. Credit: NASA

During the Hadean Eon, some 4.5 billion years ago, the world was a much different place than it is today. As the name Hades would suggest (Greek for “underworld”), it was a hellish period for Earth, marked by intense volcanism and intense meteoric impacts. It was also during this time that outgassing and volcanic activity produced the primordial atmosphere composed of carbon dioxide, hydrogen and water vapor.

Little of this primordial atmosphere remains, and geothermal evidence suggests that the Earth’s atmosphere may have been completely obliterated at least twice since its formation more than 4 billion years ago. Until recently, scientists were uncertain as to what could have caused this loss.

But a new study from MIT, Hebrew Univeristy, and Caltech indicates that the intense bombardment of meteorites in this period may have been responsible.

This meteoric bombardment would have taken place at around the same time that the Moon was formed. The intense bombardment of space rocks would have kicked up clouds of gas with enough force to permanent eject the atmosphere into space. Such impacts may have also blasted other planets, and even peeled away the atmospheres of Venus and Mars.

In fact, the researchers found that small planetesimals may be much more effective than large impactors –  such as Theia, whose collision with Earth is believed to have formed the Moon – in driving atmospheric loss. Based on their calculations, it would take a giant impact to disperse most of the atmosphere; but taken together, many small impacts would have the same effect.

Artist's concept of a collision between proto-Earth and Theia, believed to happened 4.5 billion years ago. Credit: NASA
Artist’s concept of a collision between proto-Earth and Theia, believed to happened 4.5 billion years ago. Credit: NASA

Hilke Schlichting, an assistant professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences, says understanding the drivers of Earth’s ancient atmosphere may help scientists to identify the early planetary conditions that encouraged life to form.

“[This finding] sets a very different initial condition for what the early Earth’s atmosphere was most likely like,” Schlichting says. “It gives us a new starting point for trying to understand what was the composition of the atmosphere, and what were the conditions for developing life.”

What’s more, the group examined how much atmosphere was retained and lost following impacts with giant, Mars-sized and larger bodies and with smaller impactors measuring 25 kilometers or less.

What they found was that a collision with an impactor as massive as Mars would have the necessary effect of generating a massive a shockwave through the Earth’s interior and potentially ejecting a significant fraction of the planet’s atmosphere.

However, the researchers determined that such an impact was not likely to have occurred, since it would have turned Earth’s interior into a homogenous slurry. Given the appearance of diverse elements observed within the Earth’s interior, such an event does not appear to have happened in the past.

A series of smaller impactors, by contrast, would generate an explosion of sorts, releasing a plume of debris and gas. The largest of these impactors would be forceful enough to eject all gas from the atmosphere immediately above the impact zone. Only a fraction of this atmosphere would be lost following smaller impacts, but the team estimates that tens of thousands of small impactors could have pulled it off.

An artistic conception of the early Earth, showing a surface pummeled by large impact, resulting in extrusion of deep seated magma onto the surface. At the same time, distal portion of the surface could have retained liquid water. Credit: Simone Marchi
Artist’s concept of the early Earth, showing a surface pummeled by large impacts. Credit: Simone Marchi

Such a scenario did likely occur 4.5 billion years ago during the Hadean Eon. This period was one of galactic chaos, as hundreds of thousands of space rocks whirled around the solar system and many are believed to have collided with Earth.

“For sure, we did have all these smaller impactors back then,” Schlichting says. “One small impact cannot get rid of most of the atmosphere, but collectively, they’re much more efficient than giant impacts, and could easily eject all the Earth’s atmosphere.”

However, Schlichting and her team realized that the sum effect of small impacts may be too efficient at driving atmospheric loss. Other scientists have measured the atmospheric composition of Earth compared with Venus and Mars; and compared to Venus, Earth’s noble gases have been depleted 100-fold. If these planets had been exposed to the same blitz of small impactors in their early history, then Venus would have no atmosphere today.

She and her colleagues went back over the small-impactor scenario to try and account for this difference in planetary atmospheres. Based on further calculations, the team identified an interesting effect: Once half a planet’s atmosphere has been lost, it becomes much easier for small impactors to eject the rest of the gas.

The researchers calculated that Venus’ atmosphere would only have to start out slightly more massive than Earth’s in order for small impactors to erode the first half of the Earth’s atmosphere, while keeping Venus’ intact. From that point, Schlichting describes the phenomenon as a “runaway process — once you manage to get rid of the first half, the second half is even easier.”

This gave rise to another important question: What eventually replaced Earth’s atmosphere? Upon further calculations, Schlichting and her team found the same impactors that ejected gas also may have introduced new gases, or volatiles.

“When an impact happens, it melts the planetesimal, and its volatiles can go into the atmosphere,” Schlichting says. “They not only can deplete, but replenish part of the atmosphere.”

The "impact farm:, an area on Venus marked by impact craters and volcanic activity. Credit: NASA/JPL
The “impact farm:, an area on Venus marked by impact craters and volcanic activity. Credit: NASA/JPL

The group calculated the amount of volatiles that may be released by a rock of a given composition and mass, and found that a significant portion of the atmosphere may have been replenished by the impact of tens of thousands of space rocks.

“Our numbers are realistic, given what we know about the volatile content of the different rocks we have,” Schlichting notes.

Jay Melosh, a professor of earth, atmospheric, and planetary sciences at Purdue University, says Schlichting’s conclusion is a surprising one, as most scientists have assumed the Earth’s atmosphere was obliterated by a single, giant impact. Other theories, he says, invoke a strong flux of ultraviolet radiation from the sun, as well as an “unusually active solar wind.”

“How the Earth lost its primordial atmosphere has been a longstanding problem, and this paper goes a long way toward solving this enigma,” says Melosh, who did not contribute to the research. “Life got started on Earth about this time, and so answering the question about how the atmosphere was lost tells us about what might have kicked off the origin of life.”

Going forward, Schlichting hopes to examine more closely the conditions underlying Earth’s early formation, including the interplay between the release of volatiles from small impactors and from Earth’s ancient magma ocean.

“We want to connect these geophysical processes to determine what was the most likely composition of the atmosphere at time zero, when the Earth just formed, and hopefully identify conditions for the evolution of life,” Schlichting says.

Schlichting and her colleagues have published their results in the February edition of the journal Icarus.

Further Reading: MIT News

NASA’s Next Exoplanet Hunter Moves Into Development

A conceptual image of the Transiting Exoplanet Survey Satellite. Image Credit: MIT

NASA’s ongoing hunt for exoplanets has entered a new phase as NASA officially confirmed that the Transiting Exoplanet Survey Satellite (TESS) is moving into the development phase. This marks a significant step for the TESS mission, which will search the entire sky for planets outside our solar system (a.k.a. exoplanets). Designed as the first all-sky survey, TESS will spend two years of an overall three-year mission searching both hemispheres of the sky for nearby exoplanets.

Previous sky surveys with ground-based telescopes have mainly picked out giant exoplanets. In contrast, TESS will examine a large number of small planets around the very brightest stars in the sky. TESS will then record the nearest and brightest main sequence stars hosting transiting exoplanets, which will forever be the most favorable targets for detailed investigations. During the third year of the TESS mission, ground-based astronomical observatories will continue monitoring exoplanets identified by the TESS spacecraft.

“This is an incredibly exciting time for the search of planets outside our solar system,” said Mark Sistilli, the TESS program executive from NASA Headquarters, Washington. “We got the green light to start building what is going to be a spacecraft that could change what we think we know about exoplanets.”

“During its first two years in orbit, the TESS spacecraft will concentrate its gaze on several hundred thousand specially chosen stars, looking for small dips in their light caused by orbiting planets passing between their host star and us,” said TESS Principal Investigator George Ricker of the Massachusetts Institute of Technology..

Artistic representations of the only known planets around other stars (exoplanets) with any possibility to support life as we know it. Credit: Planetary Habitability Laboratory, University of Puerto Rico, Arecibo.
Artistic representations of known exoplanets with any possibility to support life. Image Credit: Planetary Habitability Laboratory, University of Puerto Rico, Arecibo.

All in all, TESS is expected to find more than 5,000 exoplanet candidates, including 50 Earth-sized planets. It will also find a wide array of exoplanet types, ranging from small, rocky planets to gas giants. Some of these planets could be the right sizes, and orbit at the correct distances from their stars, to potentially support life.

“The most exciting part of the search for planets outside our solar system is the identification of ‘earthlike’ planets with rocky surfaces and liquid water as well as temperatures and atmospheric constituents that appear hospitable to life,” said TESS Project Manager Jeff Volosin at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Although these planets are small and harder to detect from so far away, this is exactly the type of world that the TESS mission will focus on identifying.”

Now that NASA has confirmed the development of TESS, the next step is the Critical Design Review, which is scheduled to take place in 2015. This would clear the mission to build the necessary flight hardware for its proposed launch in 2017.

“After spending the past year building the team and honing the design, it is incredibly exciting to be approved to move forward toward implementing NASA’s newest exoplanet hunting mission,” Volosin said.

TESS is designed to complement several other critical missions in the search for life on other planets. Once TESS finds nearby exoplanets to study and determines their sizes, ground-based observatories and other NASA missions, like the James Webb Space Telescope, would make follow-up observations on the most promising candidates to determine their density and other key properties.

The James Webb Space Telescope. Image Credit: NASA/JPL
The James Webb Space Telescope. Image Credit: NASA/JPL

By figuring out a planet’s characteristics, like its atmospheric conditions, scientists could determine whether the targeted planet has a habitable environment.

“TESS should discover thousands of new exoplanets within two hundred light years of Earth,” Ricker said. “Most of these will be orbiting bright stars, making them ideal targets for characterization observations with NASA’s James Webb Space Telescope.”

“The Webb telescope and other teams will focus on understanding the atmospheres and surfaces of these distant worlds, and someday, hopefully identify the first signs of life outside of our solar system,” Volosin said.

TESS will use four cameras to study sections of the sky’s north and south hemispheres, looking for exoplanets. The cameras would cover about 90 percent of the sky by the end of the mission.

This makes TESS an ideal follow-up to the Kepler mission, which searches for exoplanets in a fixed area of the sky. Because the TESS mission surveys the entire sky, TESS is expected to find exoplanets much closer to Earth, making them easier for further study.

In addition, Ricker said TESS would provide precision, full-frame images for more than 20 million bright stars and galaxies.

“This unique new data will comprise a treasure trove for astronomers throughout the world for many decades to come,” Ricker said.

Now that TESS is cleared to move into the next development stage, it can continue towards its goal of being a key part of NASA’s search for life beyond Earth.

“I’m still hopeful that in my lifetime, we will discover the existence of life outside of our solar system and I’m excited to be part of a NASA mission that serves as a key stepping stone in that search,” Volosin said.

Further Reading: NASA