The Basics

“Is there life on Mars?” is a question people have asked for more than a century. But in order to finally get the answer, we have to know what to look for and where to go on the planet to look for evidence of past life. With the Perseverance rover set to land on Mars on February 18, 2021, we are finally in a position to know where to go, what to look for, and knowing whether there is, or ever was, life on the Red Planet. Credit:  John Grant Center for Earth and Planetary Studies Si.edu https://airandspace.si.edu/stories/editorial/percy-life-on-mars

If all goes according to plan, the landing of the Mars 2020 Perseverance rover (“Percy”) tomorrow (February 18, 2021) will mark the start of NASA’s ninth surface mission on the Red Planet. Percy will touch down in Jezero crater on Mars, where she will set off exploring new and uncharted terrains in search of ancient signs of life. Nearly 60 years have passed since the first spacecraft were sent to Mars, and it’s inspiring (albeit sometimes unbelievable) to reflect on the progress that has been made since then. First, we sent spacecraft to fly-by, then to orbit, then to land, and finally to rove. As we’ve become more familiar with Mars over time, and as our technological capabilities have improved, our methods of and goals for exploration have evolved in turn.  And with each new mission, humans have pushed the boundaries a little more—or in the case of Percy, a lot more. Here I highlight three new (and particularly challenging) aspects of the Mars 2020 mission that distinguish it from previous missions and that have the potential to significantly impact the future of Mars exploration. Credits: Mariah Baker, si.edu https://airandspace.si.edu/stories/editorial/driving-mars-exploration-perseverance

After glimpsing faint but widespread super-heated material in the Sun’s outer atmosphere, a NASA sounding rocket is going back for more. This time, they’re carrying a new instrument optimized to see it across a wider region of the Sun. The mission, known as Extreme Ultraviolet Normal Incidence Spectrograph, or EUNIS for short, will launch from the White Sands Missile Range in New Mexico. The launch window opens on May 18, 2021. EUNIS is an instrument suite mounted on a sounding rocket, a type of space vehicle that makes short flights above Earth’s atmosphere before falling back to Earth. Getting to space is important, because EUNIS observes the Sun in a range of extreme ultraviolet light that does not penetrate Earth’s atmosphere. For the upcoming flight, the fourth for the EUNIS instrument, the team added a new channel to measure wavelengths between nine and 11 nanometers. (Visible light wavelengths are between 380 and 700 nanometers.)  The new wavelength range is attracting attention after an unexpected finding from EUNIS’s previous flight in 2013. Credit: NASA

What happens when two galaxies collide? One of the brightest galaxies in the night sky, Centaurus A, is well known for its distinct “S” shape. This shape is believed to be the result of a clash between a spiral and an elliptical galaxy about 100 million years ago. Now, for the first time, scientists have mapped out the invisible magnetic fields pulsing through Centaurus A using infrared light. The results show how the merging of the two original galaxies created a new, reshaped, and contorted galaxy that not only combined the two galaxies’ magnetic fields but amplified their forces. The new observations, made with NASA’s airborne Stratospheric Observatory for Infrared Astronomy, SOFIA, provide new insights into how the early universe may have been shaped by galactic mergers under the influence of their supercharged magnetic fields. The results were recently published in Nature Astronomy. “Magnetic fields were key to shaping the early universe, but they did not start out as the forces we know today; somehow they grew stronger over time,” said Dr. Enrique Lopez-Rodriguez a research scientist at Stanford Kavli Institute for Particle Astrophysics and Cosmology in Stanford, California. “Galactic mergers appear to be one of the strengthening mechanisms.” Since it is relatively close by intergalactic standards, at 13 million light-years away, Centaurus A makes a good candidate to study galactic mergers. The new view of the large-scale magnetic fields, which span  1,600 light-years, found they run parallel to the dust lanes that are remnants of the original spiral galaxy. Credit: NASA

Astronomers have detected X-rays from Uranus for the first time, using NASA’s Chandra X-ray Observatory. This result may help scientists learn more about this enigmatic ice giant planet in our solar system. Uranus is the seventh planet from the Sun and has two sets of rings around its equator. The planet, which has four times the diameter of Earth, rotates on its side, making it different from all other planets in the solar system. Since Voyager 2 was the only spacecraft to ever fly by Uranus, astronomers currently rely on telescopes much closer to Earth, like Chandra and the Hubble Space Telescope, to learn about this distant and cold planet that is made up almost entirely of hydrogen and helium. In the new study, researchers used Chandra observations taken in Uranus in 2002 and then again in 2017. They saw a clear detection of X-rays from the first observation, just analyzed recently, and a possible flare of X-rays in those obtained fifteen years later. The main graphic shows a Chandra X-ray image of Uranus from 2002 (in pink) superimposed on an optical image from the Keck-I Telescope obtained in a separate study in 2004. The latter shows the planet at approximately the same orientation as it was during the 2002 Chandra observations. What could cause Uranus to emit X-rays? The answer: mainly the Sun. Astronomers have observed that both Jupiter and Saturn scatter X-ray light given off by the Sun, similar to how Earth’s atmosphere scatters the Sun’s light. While the authors of the new Uranus study initially expected that most of the X-rays detected would also be from scattering, there are tantalizing hints that at least one other source of X-rays is present. If further observations confirm this, it could have intriguing implications for understanding Uranus. One possibility is that the rings of Uranus are producing X-rays themselves, which is the case for Saturn’s rings. Uranus is surrounded by charged particles such as electrons and protons in its nearby space environment. If these energetic particles collide with the rings, they could cause the rings to glow in X-rays. Another possibility is that at least some of the X-rays come from auroras on Uranus, a phenomenon that has previously been observed on this planet at other wavelengths. Credit: NASA

Earth is on a budget – an energy budget. Our planet is constantly trying to balance the flow of energy in and out of Earth’s system. But human activities are throwing that off balance, causing our planet to warm in response. Radiative energy enters Earth’s system from the sunlight that shines on our planet. Some of this energy reflects off of Earth’s surface or atmosphere back into space. The rest gets absorbed, heats the planet, and is then emitted as thermal radiative energy the same way that black asphalt gets hot and radiates heat on a sunny day. Eventually this energy also heads toward space, but some of it gets re-absorbed by clouds and greenhouse gases in the atmosphere. The absorbed energy may also be emitted back toward Earth, where it will warm the surface even more. Adding more components that absorb radiation – like greenhouse gases – or removing those that reflect it – like aerosols – throws off Earth’s energy balance, and causes more energy to be absorbed by Earth instead of escaping into space. This is called a radiative forcing, and it’s the dominant way human activities are affecting the climate. Climate modelling predicts that human activities are causing the release of greenhouse gases and aerosols that are affecting Earth’s energy budget. Now, a NASA study has confirmed these predictions with direct observations for the first time: radiative forcings are increasing due to human actions, affecting the planet’s energy balance and ultimately causing climate change. The paper was published online March 25, 2021, in the journal Geophysical Research Letters. “This is the first calculation of the total radiative forcing of Earth using global observations, accounting for the effects of aerosols and greenhouse gases,” said Ryan Kramer, first author on the paper and a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland, Baltimore County. “It’s direct evidence that human activities are causing changes to Earth’s energy budget.” NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project studies the flow of radiation at the top of Earth’s atmosphere. A series of CERES instruments have continuously flown on satellites since 1997. Each measures how much energy enters Earth’s system and how much leaves, giving the overall net change in radiation. That data, in combination with other data sources such as ocean heat measurements, shows that there’s an energy imbalance on our planet. “But it doesn’t tell us what factors are causing changes in the energy balance,” said Kramer. This study used a new technique to parse out how much of the total energy change is caused by humans. The researchers calculated how much of the imbalance was caused by fluctuations in factors that are often naturally occurring, such as water vapor, clouds, temperature and surface albedo (essentially the brightness or reflectivity of Earth’s surface). For example, the Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua satellite measures water vapor in Earth’s atmosphere. Water vapor absorbs energy in the form of heat, so changes in water vapor will affect how much energy ultimately leaves Earth’s system. The researchers calculated the energy change caused by each of these natural factors, then subtracted the values from the total. The portion leftover is the radiative forcing. Credit: NASA

NASA is targeting no earlier than April 8 for the Ingenuity Mars Helicopter to make the first attempt at powered, controlled flight of an aircraft on another planet. Before the 4-pound (1.8-kilogram) rotorcraft can attempt its first flight, however, both it and its team must meet a series of daunting milestones. Ingenuity remains attached to the belly of NASA’s Perseverance rover, which touched down on Mars Feb. 18. On March 21, the rover deployed the guitar case-shaped graphite composite debris shield that protected Ingenuity during landing. The rover currently is in transit to the “airfield” where Ingenuity will attempt to fly. Once deployed, Ingenuity will have 30 Martian days, or sols, (31 Earth days) to conduct its test flight campaign. “When NASA’s Sojourner rover landed on Mars in 1997, it proved that roving the Red Planet was possible and completely redefined our approach to how we explore Mars. Similarly, we want to learn about the potential Ingenuity has for the future of science research,” said Lori Glaze, director of the Planetary Science Division at NASA Headquarters. “Aptly named, Ingenuity is a technology demonstration that aims to be the first powered flight on another world and, if successful, could further expand our horizons and broaden the scope of what is possible with Mars exploration.” Flying in a controlled manner on Mars is far more difficult than flying on Earth. The Red Planet has significant gravity (about one-third that of Earth’s) but its atmosphere is just 1% as dense as Earth’s at the surface. During Martian daytime, the planet’s surface receives only about half the amount of solar energy that reaches Earth during its daytime, and nighttime temperatures can drop as low as minus 130 degrees Fahrenheit (minus 90 degrees Celsius), which can freeze and crack unprotected electrical components. To fit within the available accommodations provided by the Perseverance rover, the Ingenuity helicopter must be small. To fly in the Mars environment, it must be lightweight. To survive the frigid Martian nights, it must have enough energy to power internal heaters. The system – from the performance of its rotors in rarified air to its solar panels, electrical heaters, and other components – has been tested and retested in the vacuum chambers and test labs of NASA’s Jet Propulsion Laboratory in Southern California. “Every step we have taken since this journey began six years ago has been uncharted territory in the history of aircraft,” said Bob Balaram, Mars Helicopter chief engineer at JPL. “And while getting deployed to the surface will be a big challenge, surviving that first night on Mars alone, without the rover protecting it and keeping it powered, will be an even bigger one.” Credit: NASA

The near-Earth object was thought to pose a slight risk of impacting Earth in 2068, but now radar observations have ruled that out. After its discovery in 2004, asteroid 99942 Apophis had been identified as one of the most hazardous asteroids that could impact Earth. But that impact assessment changed as astronomers tracked Apophis and its orbit became better determined. Now, the results from a new radar observation campaign combined with precise orbit analysis have helped astronomers conclude that there is no risk of Apophis impacting our planet for at least a century. Estimated to be about 1,100 feet (340 meters) across, Apophis quickly gained notoriety as an asteroid that could pose a serious threat to Earth when astronomers predicted that it would come uncomfortably close in 2029. Thanks to additional observations of the near-Earth object (NEO), the risk of an impact in 2029 was later ruled out, as was the potential impact risk posed by another close approach in 2036. Until this month, however, a small chance of impact in 2068 still remained. When Apophis made a distant flyby of Earth around March 5, astronomers took the opportunity to use powerful radar observations to refine the estimate of its orbit around the Sun with extreme precision, enabling them to confidently rule out any impact risk in 2068 and long after. Credit: NASA

In the quest for habitable planets beyond our own, NASA is studying a mission concept called Pandora, which could eventually help decode the atmospheric mysteries of distant worlds in our galaxy. One of four low-cost astrophysics missions selected for further concept development under NASA’s new Pioneers program, Pandora would study approximately 20 stars and exoplanets – planets outside of our solar system – to provide precise measurements of exoplanetary atmospheres. This mission would seek to determine atmospheric compositions by observing planets and their host stars simultaneously in visible and infrared light over long periods. Most notably, Pandora would examine how variations in a host star’s light impacts exoplanet measurements. This remains a substantial problem in identifying the atmospheric makeup of planets orbiting stars covered in starspots, which can cause brightness variations as a star rotates. Pandora is a small satellite mission known as a SmallSat, one of three such orbital missions receiving the green light from NASA to move into the next phase of development in the Pioneers program. SmallSats are low-cost spaceflight missions that enable the agency to advance scientific exploration and increase access to space. Pandora would operate in Sun-synchronous low-Earth orbit, which always keeps the Sun directly behind the satellite. This orbit minimizes light changes on the satellite and allows Pandora to obtain data over extended periods. Of the SmallSat concepts selected for further study, Pandora is the only one focused on exoplanets. “Exoplanetary science is moving from an era of planet discovery to an era of atmospheric characterization,” said Elisa Quintana, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the principal investigator for Pandora. “Pandora is focused on trying to understand how stellar activity affects our measurements of exoplanet atmospheres, which will lay the groundwork for future exoplanet missions aiming to find planets with Earth-like atmospheres.” Credit: NASA

HUBBLE USES OUR MOON TO PROBE EARTH’S ATMOSPHERE DURING A LUNAR ECLIPSE Astronauts who have gazed at Earth from space have been awestruck at our blue marble planet's majesty and diversity. Mike Massimino, who helped service the Hubble Space Telescope in orbit, said, "I think of our planet as a paradise. We are very lucky to be here." What's mind-blowing is that astronomers estimate there could be as many as 1 billion other planets like Earth in our Milky Way galaxy alone. Just imagine, one billion – not million – other "paradise planets." But it's paradise lost if nothing is living there to marvel at sunsets in azure blue skies. And, as 19th century philosopher Thomas Carlyle mused, "…what a waste of space." It is sobering that our home planet is the only known place in the universe where life as we know it exists and thrives. And so, we gaze outward to the stars, imprisoned by space and time, into a cosmic loneliness. That's why scientists are dedicated to building ever-larger telescopes to search for potentially habitable planets. But how will they know life is present without traveling there and watching creatures walk, fly, or slither around? One way is by probing a planet's atmosphere. An atmosphere with the right mix of chemical elements is necessary to nurture and sustain life. Earth's atmosphere includes oxygen, nitrogen, methane, and carbon dioxide that have helped support life for billions of years. Earth's abundance of oxygen, especially, is a clue that our atmosphere's oxygen content is being replenished by biological processes. Astronomers have been using a variety of ground- and space-based telescopes to analyze how the ingredients of Earth's atmosphere look from space, using our planet as a proxy for studying extrasolar planets' atmospheres. They hope to eventually compare Earth's atmospheric composition with those of other worlds to note similarities and differences. Taking advantage of a total lunar eclipse, astronomers using the Hubble telescope have detected ozone in Earth's atmosphere by looking at Earthlight reflected off the Moon. Our Moon came in handy as a giant mirror in space. Ozone is a key ingredient in our planet's atmosphere. It forms naturally when oxygen is exposed to strong concentrations of ultraviolet light, which triggers chemical reactions. Ozone is Earth's security blanket, protecting life from deadly ultraviolet rays. This is the first time a total lunar eclipse was captured at ultraviolet wavelengths and from a space telescope. This method simulates how astronomers will search for circumstantial evidence of life beyond Earth by looking for potential biosignatures on extrasolar planets. Using a space telescope for eclipse observations reproduces the conditions under which future telescopes would measure atmospheres of extrasolar planets that pass in front of their stars. These atmospheres may contain chemical signatures very similar to Earth, and pique our curiosity to wonder if we are not alone in the universe. CREDITS: Science: NASA, ESA, and A. Youngblood (Laboratory for Atmospheric and Space Physics)