Like most years, 2017 saw numerous scientific advancements and discoveries throughout the solar system and beyond, most of which passed public attention with little fanfare for these discoveries that are helping to shape and build not only our knowledge of our solar system but also how to navigate the space around Earth in the safest way possible for our astronauts and spacecraft.
At the center of these discoveries was the Sun, with scientists making numerous advancements in space weather forecasting – something that will greatly aid astronauts living aboard the International Space Station as well as future crewed missions beyond Low Earth Orbit to the Moon, asteroids, and to Mars.
The dynamic environment surrounding Earth that our astronauts and spacecraft travel through can be bombarded at times by huge solar eruptions from the Sun, which spew giant clouds of magnetic energy and plasma – called Coronal Mass Ejections (CMEs) – into space.
Earlier this year, the Eruptive Event Generator (Gibson and Low), developed by a team at the University of Michigan, was designed to help map the path of potential Coronal Mass Ejections through space and their magnetic configurations when they arrive at Earth.
The new model uses calculations based on how the plasma properties and magnetic free energy, or electromagnetics, guide a Coronal Mass Ejection’s movement through space, and can help researchers better understand how the Sun will affect near-Earth space and potentially improve our ability to predict space weather.
Predicting these types of events and how strong they will be when they reach Earth is one of the multitude of things NASA monitors in regard to the permanent human presence aboard the International Space Station. If a Coronal Mass Ejection is predicted to be strong enough, the crew aboard the Station could seek shelter in either the U.S. Destiny laboratory or the Russian Zvezda service module, both of which are outfitted with more robust radiation shielding than the rest of the Station.
From a more terrestrial standpoint, understanding the exact strength and configuration of a CME when it reaches Earth would help provide better warnings on the effects a Coronal Mass Ejection might have on our fleet of orbiting satellites, telecommunication services, and GPS navigational aids – all of which hold the potential to be disrupted by strong Coronal Mass Ejection tantrums from the Sun.
In addition to this new model, direct observation of the Sun also helped NASA and space weather researchers refine their forecasting tools for such Coronal Mass Ejection events – by linking them to a well-studied atmospheric phenomenon on Earth.
According to new research released in March, scientists discovered a phenomenon on the surface of the Sun similar to a common weather system seen on Earth, where influence from jet streams create atmospheric currents that result in a phenomenon known as Rossby waves – wind currents in Earth’s atmosphere driven by the planet’s rotation.
Using comprehensive imaging of the entire Sun with data from the NASA heliophysics Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory, scientists have found proof of Rossby waves on the Sun – driven by magnetic currents instead of wind currents.
“It’s not a huge surprise that these things exist on the Sun. The cool part is what they do,” said lead author of the study Scott McIntosh, director of the High Altitude Observatory at the National Center for Atmospheric Research in Boulder, Colorado. “Just like the jet stream and the gulf stream on Earth, these guys on the Sun drive weather – space weather.”
Of particular importance to this discovery, understanding solar Rossby waves and the interior processes that drive them may allow solar scientists to predict when solar flares might occur. Currently, we can forecast the short-term effects after a solar flare erupts, but we cannot predict the appearance of the flare itself.
Now, by studying solar Rossby waves, we might be able to predict solar flares before they appear, an invaluable tool for terrestial- and space-based communications and navigation equipment as well as for our astronauts on Station and for future interplanetary crewed missions which will fly through regions unprotected from the damaging energetic particles flares can release.
Additionally, imaging of solar Rossby waves revealed trains of coronal brightpoints – small, luminous features on the Sun – that are directly linked to magnetic activity beneath the solar surface. The brightpoints shed light on the solar cycle, which is driven by the constant movement of magnetic material inside the Sun, and may serve as a clue to how the solar cycle leads to increased numbers of solar flares every 11 years.
A particularly active part of the solar cycle back in 2014 yielded a Coronal Mass Ejection that scientists this year were able to trace throughout the solar system using 10 NASA and European Space Agency (ESA) spacecraft.
By utilizing spacecraft deployed throughout the solar system, scientists were able to trace a single CME from its origination at the Sun on 14 October 2014 through its outward journey to the Voyager 2 spacecraft on 26 March 2016 when the craft was 111 AU from the Sun.
This ability to trace and measure particle detection outward to 111 AUs greatly added to the database of CME information scientists use to understand how charged particles interact with various regions of the solar system and other planets’ (Mars and Saturn) magnetic fields.
Closer to home, advancements in space weather forecasting took the form of investigation of a different type of wave – plasmaspheric hiss.
The space surrounding Earth is filled with restless charged particles and electric and magnetic fields that create waves around our planet. Plasmaspheric hiss is one example of this kind of wave and is highly important as it removes the charged particles that can interfere with satellites and telecommunications on Earth from the Van Allen radiation belts.
Now, a new study published in July using data from NASA’s Van Allen Probes identified a new population of hiss waves at a lower frequency than usually studied. These low-frequency hiss waves are a separate and unique population that cluster in different regions around Earth compared to their high-frequency counterparts.
“We found the low frequency hiss interacts more effectively with higher energy electrons and can knock those electrons out of the belts more efficiently,” said David Malaspina, lead author and researcher of the study at the Laboratory for Atmospheric and Space Physics in Boulder, Colorado. “You want to know the state of the Van Allen radiation belts so you know how long satellites will last, and part of that is understanding the state of [these hiss] waves.”
Understanding how both the low-frequency and high-frequency hiss waves interact with higher energy electrons will allow scientists to create better space weather forecasts and will provide spacecraft builders with better information on how long and in what space weather conditions their satellites will operate in.
Moreover, new research this year also revealed space weather’s effects on our closest celestial neighbor: the Moon.
According to new information released in January 2017, NASA funded research indicated that powerful solar storms can charge up the soil in frigid, permanently shadowed regions near the lunar poles – a charge that could produce a “spark” that could vaporize and melt the lunar soil.
This vaporizing of the lunar surface material, called regolith, is a known occurrence due to meteoroid impacts. “About 10 percent of [the regolith] layer has been melted or vaporized by meteoroid impacts,” said Andrew Jordan of the University of New Hampshire, Durham. With new research, however, Mr. Jordan’s team “found that in the Moon’s permanently shadowed regions, sparks from solar storms could melt or vaporize a similar percentage” of the lunar regolith.
Explosive solar activity, like flares and Coronal Mass Ejections, blasts highly energetic, electrically charged particles into space. Earth’s atmosphere shields us from most of this radiation, but on the Moon, these particles – ions and electrons – slam directly into the surface and accumulate in two layers beneath the surface.
Since the bulky ions can’t penetrate deeply because they are more likely to hit atoms in the regolith, they form a layer closer to the surface while the tiny electrons slip through and form a deeper layer. The bulky ions have a positive charge while the electrons carry a negative charge. Since opposite charges attract, normally these charges flow towards each other and balance out.
However, Mr. Jordan’s team predicts that strong solar storms would cause the regolith in the Moon’s Permanently Shadowed Regions (PSRs) to accumulate charge in these two layers until explosively released, like a miniature lightning strike. This is because the permanently shadowed regions are so frigid that regolith becomes an extremely poor conductor of electricity.
Therefore, during intense solar storms, the lunar regolith is expected to dissipate the build-up of charge too slowly to avoid the destructive effects of a sudden electric discharge, called dielectric breakdown.
“This process isn’t completely new to space science – electrostatic discharges can occur in any poorly conducting (dielectric) material exposed to intense space radiation, and is actually the leading cause of spacecraft anomalies,” said Timothy Stubbs of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
More importantly, understanding this phenomenon is vitally important to future missions and colonization efforts of the Moon as several of the permanently shadowed regions of lunar north pole craters are known to contain water ice.
Additionally, research from Mr. Jordan’s team indicates that the lunar night – which lasts two weeks – might allow other regions of the Moon to become cold enough that their susceptibility to this type of explosive breakdown increases – something that needs to be understood as part of humanity’s lunar colonization efforts and understanding of how solar storms and solar radiation may affect us outside of Earth’s protective magnetic field.
Unlike Earth, the Moon does not have a magnetic protection field surrounding it; but new research published this year indicates that heat from crystallization at the lunar core may have driven the Moon’s now-defunct magnetic field nearly 3 billion years ago.
Soil samples and rocks returned during the six Apollo lunar landing missions confirmed that the Moon once had a magnetic field that lasted for more than a billion years and was – at one point – equal to that of modern Earth’s.
At the time of the discovery, scientists believed that a lunar dynamo – a molten, churning core at the center of the Moon – may have been the source of the magnetic field, but scientists did not understand how that molten churning core was generated or maintained.
The issue was that modeling of the Moon involved an iron/nickel core with sulfur contents so high (and melting point so low) that crystallization would not have occurred until very late in lunar history. Thus the source of the heat flow out of the core required to drive a dynamo was unclear.
Now, evidence is emerging that this dynamo was indeed caused by the crystallization of the lunar core. According to a paper published in Earth and Planetary Science Letters, scientists in the Astromaterials Research and Exploration Science (ARES) Division at NASA’s Johnson Space Center in Houston, the Moon likely had an iron/nickel core with only a small amount of sulfur and carbon, thus giving the lunar core a high melting point.
As a result, the core likely started crystallizing early in lunar history, and the heat released by crystallization may have driven an early magnetic field that is recorded in ancient lunar samples. This new lunar core composition proposed by the ARES group would be partially solid and liquid today, consistent with current lunar seismic, geophysical, and spacecraft data.
From the core to the lunar surface, 2017 also brought a new understanding of where the moon’s water ice may have originated. New information from NASA’s Marshall Space Flight Center and the Lunar and Planetary Institute in Houston, Texas, reveals the potential that billions of years ago the Moon had a significant atmosphere that could likely be the source of most – if not all – of the water detected on the Moon.
The new information, compiled in part by studying the iron and magnesium-rich volcanic rocks returned to Earth by the Apollo crews, indicates that the Moon had a short-lived atmosphere comprised primarily of carbon monoxide, sulfur, and water – and that these elements were released into the atmosphere by volcanic eruptions 3.9 to 1 billion years ago.
The researchers discovered that so much water was released during the eruptions that if just 0.1% of the erupted water migrated to the permanently shadowed regions on the Moon, it could account for all of the water detected there.
Water is one of the keys to living off of the land in space, called in-situ resource utilization – and understanding where the lunar water came from, either from inside the Moon or from asteroid bombardment, helps scientists and mission planners know if the resource is renewable or limited.
However, a potential issue for in-situ resource utilization on the surface of the Moon is quite literally how different things look on the lit portions of the Moon versus the shadowed portions of the lunar surface.
On Earth, shadows in otherwise bright environments are dimly lit with indirect light from tiny reflections of dust particles in the atmosphere, and that provides enough detail to allow an observer an idea of shapes, holes, and other features that could be obstacles to someone – or a robot – trying to maneuver in shadow.
But on the Moon, which isn’t big enough to hold a significant atmosphere, there is no air and there are no particles in the air to reflect and scatter sunlight. So the contrast between dark and light is more than our eyes and robotic camera eyes can adjust for.
Future lunar rovers may target unexplored polar regions of the Moon to drill for water ice and other volatiles that are essential for human exploration missions. But at the Moon’s poles, the Sun is always near the horizon and long shadows hide many potential dangers in terrain like rocks and craters. Pure darkness is a challenge for robots that need to use visual sensors to safely explore the surface.
“It’s very difficult to be able to perceive anything for a robot or even a human that needs to analyze these visuals because cameras don’t have the sensitivity to be able to see the details that you need to detect a rock or a crater,” said said Uland Wong, a computer scientist at NASA’s Ames Research Center in Silicon Valley.
To combat this issue, Mr. Wong and his team in the Ames’ Intelligent Robotics Group are using simulated lunar soil and lighting to create similarly dark conditions here on Earth. “We’re building these analog environments here and lighting them like they would look on the Moon with solar simulators, in order to create these sorts of appearance conditions.”
The result of this research and simulation is a Polar Optical Lunar Analog Reconstruction dataset that provides standard information for rover designers and programmers to develop algorithms and set up sensors to help future rovers “see” potentially hidden dangers in shadowed regions on the Moon.
This database is useful not just for land-based exploration of the Moon but also for future missions to bodies away from Earth, such as asteroids and regolith-covered moons like Mars’ Phobos.
(Part II of NASASpaceflight.com’s space science Year In Review series will be published in the coming days.)