Asteroid-bound spacecraft slingshots past Earth

Gravity assist will alter its trajectory while saving fuel.

Traveling through space at 19,000 miles (30,000 km) per hour, NASA’s Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft is flying by Earth on Friday, September 22, using the planet’s gravity to redirect its path to the asteroid Bennu.

Launched a year ago from Cape Canaveral on an Atlas V rocket, the spacecraft will arrive at Bennu in November 2018. It will orbit the asteroid, identify ideal surface locations for collecting samples, then use a robotic arm to reach into the surface to take the samples and store them inside a special collection device.

In 2021, OSIRIS-REx will head back toward Earth where, two years later, it will return the samples by parachuting a canister containing them into Utah.

From there, they will be taken to NASA’s Johnson Space Center in Houston, where scientists will analyze them for organic molecules and materials that make up the building blocks of life.

An Earth flyby is necessary to propel OSIRIS-REx to its target because a direct flight would have required additional fuel that would have mandated it launch on a larger rocket.

“It was a way to substantially save on resources, either on the spacecraft or on the launch vehicle, or both,” said mission principal investigator Dante Lauretta of the University of Arizona.

The flyby, which takes the probe within about 11,000 miles (17,000 km) of Earth’s surface, will increase its velocity by 8,400 miles per hour.

NASA will be out of contact with the probe for about an hour during closest approach while it flies over Antarctica.

“OSIRIS-REx uses the Deep Space Network to communicate with Earth, and the spacecraft will be too low relative to the southern horizon to be in view with either the Deep Space tracking station at Canberra, Australia, or Goldstone, California,” explained Mike Moreau, NASA Goddard Space Flight Center flight dynamics system lead.

The spacecraft will photograph the Earth and Moon with its three imaging cameras for as long as 10 days after the flyby.

Earth data will be collected by its thermal emission spectrometer and visible and infrared spectrometer for instrument calibration purposes.

Members of the mission team plan to release photographs collected by the probe on Tuesday, September 26.

Asteroid that will fly close to Earth on Thursday poses no danger

Astronomers will have opportunity to observe a complete rotation of the object in just one night.

An asteroid discovered five years ago will come within 31,000 miles (50,000 km) of Earth on Thursday, October 12, but poses no impact danger to our planet.

Just a week after its discovery by Hawaii’s Pan-STARRS,¬†asteroid 2012 TC4 passed within 58,900 miles (94,800 km) of Earth, and observation over time indicates it has made many such approaches in the past.

Approximately the size of the meteor that hit Chelyabinsk, Russia, in 2013, with a diameter ranging from 26 to 85 feet (8 to 26 meters), 2012 TC4 has an elongated shape, rotates at a high speed, and orbits the Sun every 1.67 years. Its distance from the Sun is around 1.4 AU or astronomical units, with one AU equal to the average Earth-Sun distance or 93 million miles.

“There is no hazard in its upcoming pass or anytime in the near future,” said Alan Harris, formerly a researcher at NASA’s Jet Propulsion Laboratory (JPL).

Early calculations conducted this summer by JPL led scientists to believe 2012 TC4 could come as close as 4,200 miles (6,800 km). Because these calculations were based on just seven days of tracking the asteroid, later studies by the European Space Agency’s (ESA) Oliver Hainaut, Detlef Koschny, and Marco Micheli using the European Southern Observatory (ESO) concluded its approach would not be that close.

According to JPL, “The new calculations indicate that TC4 will fly safely past our planet on Oct. 12, at a distance of about 43,500 km (27,000 miles) above the surface, or about one-eighth of the distance to the Moon.”

Astronomers around the world will be able to observe the asteroid, which will have a brightness of approximately magnitude 14, when it makes its close approach at 5:41 UTC (1:41 AM EDT) on Thursday.

Because 2012 TC4 has such a fast rotation rate, observers should be able to watch a full rotation in just one night, Harris said.

The International Asteroid Warning Network, a UN-sanctioned organization that focuses on collecting data on asteroids that pose potential threats to Earth, will also be following it.

While there is no chance of 2012 TC4 hitting the Earth, even if it did impact, it is too small to cause major damage and would likely land harmlessly over one of Earth’s oceans, Harris noted.

Arecibo Observatory damaged by Hurricane Maria

Officials have yet to assess damage, as roads to the site remain impassable.

Puerto Rico’s Arecibo Observatory, home of the world’s second largest radio telescope, used for research in radio astronomy and study of Earth’s atmosphere, sustained damage when Hurricane Maria battered the island last week.

The telescope’s 1,000-foot (300-meter) dish reflector was pierced several times by a 96-foot (29-meter) line feed antenna that tumbled from a height of more than 328 feet (100 meters), where it had been suspended.

That particular line feed was used largely for atmospheric research. It transmitted and received radio waves at 430 MHz.

Arecibo’s weather station measured 78 mile (126 km) per hour winds on Wednesday, September 20, and gusts up to 108 miles (174 km) per hour.

Also destroyed was a 39-foot (12 meter) dish that served as a phase reference for Very Long Baseline Interferometry (VLBI).

VLBI is a technique in which many separate radio telescopes are linked together in a network to function as a single, more powerful telescope.

In preparation for the storm, observatory staff had secured all facilities and equipment. Similar preparations had been made two weeks earlier in expectation of Hurricane Irma, but that storm took a different trajectory and did not hit Puerto Rico directly.

Staff members who remained at the facility during the hurricane are all safe. The Universities Space Research Association (USRA), one of several organizations that manage Arecibo Observatory for the National Science Foundation, is attempting to contact employees who rode out the storm in their homes or in shelters to make sure they are unharmed.

Because the island has no power, the observatory’s phone and Internet are out. All communication to and from the site is being conducted via shortwave radio.

Transportation for those not on site remains impossible because the area’s roads are filled with debris.

“We will need a full assessment of the damage, repairs that are needed, and when the observatory can resume operations,” said USRA senior vice president for science Nicholas White.

Built in the 1960s, Arecibo has been used to study a wide range of astronomical objects, from black holes and dark matter to pulsars, galaxies, planets, and asteroids.

It has sent signals into space to search for intelligent alien life and also monitored incoming signals in an attempt to determine whether any might be coming from extraterrestrial civilizations.

Arecibo’s visitor center will be closed at least through Wednesday, September 27.

 

 

Ocean worlds could be habitable for long periods of time

Climates can be kept stable by processes other than those that occur on Earth.

Water worlds, planets covered with oceans, could be habitable for life for more than a billion years, according to a new study that conducted over a thousand computer simulations.

Until recently, scientists thought that the only planets capable of supporting life are Earth-like worlds that have land and shallow oceans. Planets completely covered in oceans do not cycle minerals and gases, a phenomenon that keeps Earth’s climate stable.

Over very long periods of time, Earth keeps itself cool by pulling atmospheric greenhouse gases into minerals, then warms itself up by releasing the gases back into the atmosphere through volcanic eruptions.

With telescopes growing more powerful, scientists have discovered numerous exoplanets orbiting stars other than the Sun. Many of these are not at all Earth-like, and some are covered in oceans with depths of up to several hundred miles.

On ocean worlds, Earth’s method of maintaining a stable climate would not work, as all the rock is covered by water, which also suppresses volcanoes.

Edwin Kite of the University of Chicago and Eric Ford of Pennsylvania State University decided to research whether ocean worlds might use a different method to maintain climate stability. They turned to a computer simulation that tracked the evolution of thousands of planets over several billion years.

The computer model showed that if planets are in ideal orbits around their parent stars, have the right amount of carbon, begin their lives with sufficient water, and cycle carbon between their atmospheres and oceans in just the right amounts, they can maintain stable climates.

Additionally, the planets cannot have too many minerals and elements dissolved in their oceans, as these would remove atmospheric carbon.

“The surprise was that many of them stay stable for more than a billion years, just by luck of the draw. Our best guess is that it’s on the order of 10 percent of them,” Kite said.

“How much time a planet has is basically dependent on carbon dioxide and how it’s partitioned between the ocean, atmosphere, and rocks in its early years. It does seem there is a way to keep a planet habitable long-term without the geochemical cycling we see on Earth,” he added.

While the simulations were done for planets orbiting Sun-like stars, their results could also apply to those orbiting smaller, dimmer red dwarf stars.

Findings of the study have been published in the Astrophysical Journal.