No Humanoid on Mars, Just Rocks

Okay, once and for all, let’s make this clear. In the words of our esteemed Bad Astronomer, Phil Plait, “repeat after me:” A humanoid was not photographed on the surface of Mars. And NASA is not covering up this photo in the name of national security. Furthermore, human missions to Mars have not been cancelled because of this photo. These outrageous notions keep popping up in the media. The photograph, which was taken by Spirit, one of the Mars Exploration Rovers, is just another example of pareidolia, our ability to see patterns in random shapes.

As happens frequently, people tend to see faces or human forms in things like clouds, wood grain, and pancakes. This is only an optical illusion. If you need proof of this, for those of you in the US, look at one of the state-themed quarters from New Hampshire. There you can see the Man in the Mountain, a case of pareidolia that became an historic site (which has since crumbled.)

The photo shown here is the very large panoramic image from which a teeny, tiny rock formation was found that looks kind of human-like. Someone had to be looking really close to see it, as the rock formation is only about 6 centimeters high, and in the image you can also see a hill that’s over 8 kilometers (5 miles) away.

If you have any doubts in your mind that this is nothing more than just a very small, unusual rock formation, please, please, please see Emily Lakdawalla’s thorough explanation of the image at the Planetary Society’s website, which includes 3-D pictures that really make it clear this is not a humanoid. It’s a rock with a funny shape. And Phil the Bad Astronomer has more info on it as well here and here.

And, okay, here’s the really zoomed in image crop that has caused such a hubbub. Just remember how small this rock really is.
tiny detail from a panorama taken by the Mars Exploration Rover Spirit on sol 1,366-1,369 (November 6-9, 2007) of its position on the eastern edge of Home Plate. Credit: NASA / JPL / Cornell

Astronomers Could Detect Oceans on Extrasolar Planets

Imagine if astronomers could tell the difference between Earth-like extrasolar planets just by seeing the reflected light from their oceans? That sounds like science fiction, but a team of researchers have proposed that it’s really possible to detect the shape of the light curve glinting off an extrasolar planet and know if it has oceans.

This ground-breaking (water splashing?) idea was written in a recent journal article by D.M. Williams and E. Gaidos, entitled Detecting the Glint of Starlight on the Oceans of Distant Planets published January, 2008 in the Arxiv prepress e-Print archive.

The article describes the methods astronomers could use to detect the glint, or water reflection, from the “disk-averaged signal of an Earth-like planet in crescent phase.” They used the Earth as an example, and generated a series of light curves for a planet with our orientation and axial tilt.

They calculated that planets partially covered by water should appear much brighter when they’re near the crescent phase because light from the parent star reflects off the oceans very efficiently at just the right angles. By watching an extrasolar planet move through its orbit, its light curve should give off the telltale signature that there are oceans present.

According to their calculations, this method should work for about 50% of the visible planets. Furthermore, it should be possible to measure the ratio of land to water, and even get a sense of continents.

In order to test their theories, they’re planning to use remote observations of Earth, using interplanetary spacecraft. This will demonstrate if Earth can be observed at extreme phase angles—orbiting spacecraft around or on route to Mars.

And then the upcoming planet hunting missions, such as Darwin and the Terrestrial Planet Finder (if it ever gets completed) should be able to make the direct analysis of Earth-sized worlds orbiting other stars. Just by measuring the brightness, they should know if there are oceans, boosting the prospects for life.

Original Source: Arxiv

Ice Clouds on Mars Create Shade

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Until now, Mars has generally been regarded as a desert world, where a visiting astronaut would be surprised to see clouds drifting across the orange sky. But new data and images show that Mars does indeed have clouds, and some are actually thick enough to cast a shadow on the planet’s surface. These are clouds of dry ice, or carbon dioxide (CO2), and sometimes they are so large and so dense that they throw quite dark shadows on the dusty surface. This, in turn, can affect the weather patterns on Mars. Researchers also say this discovery could help to understand Mars’ climate history.

Data obtained from ESA’s Mars Express OMEGA Visible and Infrared Mineralogical Mapping Spectrometer instrument has been analyzed by a group of French scientists.

“This is the first time that carbon dioxide ice clouds on Mars have been imaged and identified from above,” said Franck Montmessin of the Service da Aeronomie, University of Versailles. “This is important because the images tell us not only about their shape, but also their size and density.”

Clouds of water ice particles have previously been seen, for example on the sides of the giant Martian volcanoes. There have also been hints of much higher, wispy clouds made up of carbon dioxide (CO2) ice crystals. This is not too surprising, since the thin Martian atmosphere is mostly made of carbon dioxide, and temperatures on the fourth planet from the Sun often plunge well below the ‘freezing point’ of carbon dioxide. But these clouds are not very thick.

But the CO2 clouds detected by OMEGA are very different. Not only are they surprisingly high — more than 80 km above the surface — but they can be several hundred kilometers across. They are also much thicker than expected. Instead of looking like the wispy ice clouds seen on Earth, they resemble tall convectional clouds that grow as the result of rising columns of warm air.

Even more surprising is the fact that the CO2 ice clouds are made of quite large particles – more than a micron (one thousandth of a millimeter) across — and they are sufficiently dense to noticeably dim the Sun. Normally, particles of this size would not be expected to form in the upper atmosphere or to stay aloft for very long before falling back towards the surface.

“The clouds imaged by OMEGA can reduce the Sun’s apparent brightness by up to 40 per cent,” said Montmessin. “This means that they cast quite a dense shadow and this has a noticeable effect on the local ground temperature. Temperatures in the shadow can be up to 10 degrees C cooler than their surroundings, and this in turn modifies the local weather, particularly the winds.”

Since the CO2 clouds are mostly seen in equatorial regions, the OMEGA team believes that the unexpected shape of the clouds and large size of their ice crystals can be explained by the extreme variations in daily temperature that occur near the equator.

“The cold temperatures at night and relatively high day-time temperatures cause large diurnal waves in the atmosphere,” explained Montmessin. “This means there is a potential for large-scale convection, particularly as the morning Sun warms the ground.”

“This discovery is important when we come to consider the past climate of Mars,” Montmessin continued. “The planet seems to have been much warmer billions of years ago, and one theory suggests that Mars was then blanketed with CO2 clouds. We can use our studies of present-day conditions to understand the role that such high level clouds could have played in the global warming of Mars.”

Original News Source: ESA Press Release

Asteroid 2007 WD5 Won’t Hit Mars

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Sorry to disappoint those of you hoping for some Martian fireworks the end of this month. NASA’s Near Earth Object (NEO) Program office has effectively ruled out the possibility of Asteroid 2007 WD5 impacting Mars. The probability of such an event has dropped dramatically, to approximately 0.01% or 1 in 10,000 odds of an impact. Observers also say the asteroid has no possibility of impact with either Mars or Earth anytime in the next century.

Recent tracking measurements of the asteroid from several Earth-based observatories have provided a significant reduction in the uncertainties of the asteroid’s position during its close approach to Mars on Jan. 30, 2008. The best estimates now have 2007 WD5 passing about 26,000 km (16,155 miles) from the planet’s center at approximately 12:00 UTC (4:00 am PST) on Jan. 30th. The NEO office at the Jet Propulsion Laboratory has 99.7% confidence that the pass should be no closer than 4000 km (2,485 miles) from Mars’ surface.

The 50 meter (164 feet) wide asteroid was discovered in late November of 2007 by astronomers at the University of Arizona as part of the Catalina Sky Survey. Other telescopes used to track the asteroid are the Kitt Peak telescope in Arizona, the Sloan Digital Sky Survey telescope in New Mexico, New Mexico Tech’s Magdalena Ridge Observatory, the Multi-Mirror Telescope in Arizona, the Mauna Kea telescope in Hawaii and the Calar Alto Observatory in Spain.

An impact on Mars by 2007 WD5 could have created a .8 km (1/2 mile) wide crater on the planet’s surface. Many scientists were excited by the prospect of such an event, one that could possibly be tracked by the many spacecraft orbiting and on the surface of the red planet.

NASA’s Spaceguard Survey continually searches for Near-Earth Asteroids such as 2007 WD5, and their goal is to discover 90% of those larger than 1 km in size. JPL’s NEO office says that goal should be met within the next few years. Each discovered asteroid is continually monitored for the possibility of impact on Earth.

Original News Source: Near Earth Object Program press release

Landing Sites for Mars Science Lab Narrowed to Six

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Where should the next spacecraft land on Mars? The Mars Science Laboratory (MSL) rover is scheduled to launch in the fall of 2009. MSL is a long-range rover that will explore a region on Mars with the goal of determining if Mars has or ever had conditions capable of supporting microbial life. Over fifty landing sites have been proposed by various planetary scientists, and recently, the selection committee narrowed the field down to six possible sites. The final site and a backup will be selected in September of 2008. Here’s a look at the six final candidates:

Mawrth Vallis: Location:Northern Plains, east of Pathfinder rover site (24.65°N, 340.10°E)
Mars Global Surveyor MOLA Instrument
This is an ancient channel carved by catastrophic floods. Spectrometers on the Mars Reconnaissance Orbiter (MRO) have detected clay minerals which contain water, and may also preserve organic materials, so there is great interest in studying these deposits to understand past environments that could have supported life. Images from the MRO HiRise camera show hills with several layers and intriguing boulders.

Nili Fossae Trough: Location: Near Isidis Planitia, and near the Beagle 2 intended landing site. (21°N, 74.2°E)
Nilli Fossae Trough.  Image Credit:  Mars Global Surveyor MOLA Instrument
This region has one of the largest and most diverse exposures of clays minerals that have been detected from orbit. Again, clay minerals contain water, and possibly organic materials. The area is a linear depression about 25 km wide that was created from tectonic activity.

Holden Crater: Location: South of Vallis Marineris (26.4°S, 325.3°E)
Holden Crater.  Image Credit:  Mars Global Surveyor MOLA Instrument
This crater contains deep gullies carved by running water as well as examples of what are assumed to be lake beds and sediments deposited by streams. These deposits are more than three billion years old, which dates back to a wetter period on Mars. Scientists believe Holden Crater once was a lake, and when the water disappeared, wind eroded the surface and formed the ripples and dunes that have been imaged by the HiRise instrument.

Eberswalde Crater: Location: South of Vallis Marineris (23.20°S, 326.75°E)
Eberswalde Delta.  Image Credit:  Mars Global Surveyor MOLA Instrument
The Eberswalde delta is the most convincing evidence on Mars for the persistent flow of a river into a standing body of water. HiRise images show many channels within the delta that have become inverted, which occurs as sediments deposited by flowing water solidify over time and become resistant to erosion. High resolution HiRise images show individual boulders breaking off from the channel deposits.

Miyamoto Crater: Location: Merdiani Planum, near Opportunity Rover site. (1.7°S, 352.4°E)
Miyamato Crater.  Image Credit:  Mars Global Surveyor MOLA Instrument
Located along the western boundary of Meridiani Planum, this 150-km crater has hematite and sulfate-bearing minerals, possibly created from lakes or groundwater. The southwestern part of the crater floor has been stripped by erosion, revealing clay minerals.

Northern Meridiani: Location: Meridiani Planum,2.34°N, 6.69°E
Meridiani.  Image Credit:  Mars Global Surveyor MOLA Instrument
This is the same area that the Opportunity rover has studied. By landing here, the MSL rover could increase our knowledge of the Meridiani region, which Opportunity has revealed to have a complex geologic history that involves flowing water, groundwater, lakes and wind. If chosen as a landing site, the MSL rover would study the smooth plains before driving to the ridged plains to the north.

MSL will arrive on Mars in 2010. Once on the surface, the rover will be able to roll over obstacles up to 75 centimeters (29 inches) high and travel up to 90 meters (295 feet) per hour. On average, the rover is expected to travel about 30 meters (98 feet) per hour, based on power levels, slippage, steepness of the terrain, visibility, and other variables. The science instruments on board include cameras, spectrometers, radiation detectors and environmental sensors.

Original News Source: HiRise Blog

1-in-75 Chance Of Tunguska-Size Impact On Mars

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A 164-foot (50 meter) wide asteroid will be crossing the orbit of Mars at the end of January 2008. Currently, there is a 1-in-75 chance of the “Mars Crosser” hitting the Red Planet, and if it does, the 30,000 mile per hour speeding mass would generate a three megaton explosion (approximately the size of the terrestrial Tunguska impact over Siberia in 1908) and create a crater half-a-mile wide somewhere north of Meridiani Planum. So, the Mars Rover Opportunity will get a ringside seat should this once-in-a-thousand-year event occur…

NASA’s Near-Earth Object Office at the Jet Propulsion Laboratory (JPL) in Pasadena, California reported this month that a known Near Earth Asteroid (NEO) will be crossing the path of Mars on January 30, 2008. This puts asteroid “2007 WD5” in a special group of asteroids: “Mars Crossers“. NASA’s Near Earth Object Observation Program (or “Spaceguard” program) is intended to track asteroids that come close to the orbit of Earth, but also provides data for any asteroids tracked near our planetary neighbors.

Scientists are both excited and concerned by the possibility of an impact on Mars. Whilst this is a once in a lifetime opportunity to observe an impact of this size on Mars (remember the excitement at Shoemaker-Levy hitting Jupiter in 1994?), this event would eject millions of tons of dust into the Mars atmosphere, interfering with the Mars Expedition Rovers, and hindering orbital imaging of the planet. The Phoenix mission (currently en-route) will undoubtedly be affected. Looking far into the future, this event could have serious consequences for manned exploration.

“Right now asteroid 2007 WD5 is about half-way between the Earth and Mars and closing the distance at a speed of about 27,900 miles per hour […] Over the next five weeks, we hope to gather more information from observatories so we can further refine the asteroid’s trajectory,” – Don Yeomans, manager of the NEO Office at JPL.

Although the odds are low, and the asteroid is expected to miss Mars by 30,000 km, asteroid hunters will be keeping a close eye on the progress of 2007 WD5 as it barrels closer and closer to the Red Planet and our robotic explorers.

Source: Near Earth Object Program

The Spirit Rover’s Big Discovery

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Amazingly, the two Mars rovers, Spirit and Opportunity, have been working diligently on the surface of the Red Planet for almost four years now. So far, Opportunity has grabbed most of the spotlight, finding evidence for past water on Mars within months after landing on the smooth plains of Meridiani Planum. While Spirit has been working just as hard, if not harder, climbing hills and traversing the rocky terrain of Gusev Crater, she hasn’t yet caused quite the stir that her twin has. But now, a recent discovery by Spirit at an area called Home Plate has researchers puzzling over a possible habitat for past microbial organisms.

What Spirit found is a patch of nearly pure silica, a main ingredient in window glass.

“This concentration of silica is probably the most significant discovery by Spirit for revealing a habitable niche that existed on Mars in the past,” said Steve Squyres, principal investigator for the rovers’ science payload.

The silica could have been produced from either a hot-spring type of environment or another type of environment called a fumarole, where acidic steam rises through cracks in the planet’s surface. On Earth, both of these types of environments teem with microbial life.

“The evidence is pointing most strongly toward fumarolic conditions, like you might see in Hawaii and in Iceland,” said Squyres. “Compared with deposits formed at hot springs, we know less about how well fumarolic deposits can preserve microbial fossils. That’s something needing more study here on Earth.”

Squyres said the patch that Spirit has been studying is more than 90 percent silica, and that there aren’t many ways to explain such a high concentration. One way is to selectively remove silica from the native volcanic rocks and concentrate it in the deposits Spirit found. Hot springs can do that, dissolving silica at high heat and then dropping it out of solution as the water cools. Another way is to selectively remove almost everything else and leave the silica behind. Acidic steam at fumaroles can do that. Scientists are still assessing both possible origins.

One reason Squyres favors the fumarole story is that the silica-rich soil on Mars has an enhanced level of titanium. On Earth, titanium levels are relatively high in some fumarolic deposits.

Meanwhile both rovers are hunkering down for another winter season on Mars. Spirit’s solar panels are currently coated with dust from the huge dust storm the rovers endured this summer, and Spirit will need to conserve energy in order to survive the low light levels during the winter.

“The last Martian winter, we didn’t move Spirit for about seven months,” said John Callas, project manager for the rovers. “This time, the rover is likely to be stationary longer and with significantly lower available energy each Martian day.”

I’m keeping my fingers crossed for another solar panel cleaning windstorm event, which has happened previously, giving the rovers a boost in power.

Original News Source: Jet Propulsion Laboratory News Release

Building Blocks of Life Can Form on Cold, Rocky Planets — Anywhere

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Our old friend and headline-maker is back in the news. Meteorite ALH84001 — the Mars rock that sent the world of astrobiology into a tizzy back in 1996 — hasn’t been just sitting around collecting dust. Researchers have been re-examining the famous meteorite in an effort to learn more about the early history of Mars. Not only did ALH84001 help determine that the building blocks of life actually did form on early Mars, but also that those same building blocks have the potential to form on a cold rocky planet anywhere in the Universe.

The meteorite, found in the Alan Hills region of Antarctica, grabbed the headlines over 11 years ago when scientists claimed to have found the remains of bacteria-like life forms within the rock from Mars. The claims have been hotly debated, with both sides still holding firm in their convictions.

But scientists at the Carnegie Institution’s Geophysical Laboratory took the research into ALH84001 a step further, and have shown for the first time that building blocks of life formed on Mars early in its history. Organic compounds that contain carbon and hydrogen form the building blocks of all life here on Earth. Previously, some scientists thought that organic material in ALH84001 was brought to Mars by meteorite impacts, and others felt the material might have originated from ancient Martian microbes, while still others thought any organics in the rock probably were introduced after it arrived on Earth.

The Carnegie-led team made a comprehensive study of the ALH 84001 meteorite and compared the results with data from related rocks found on Svalbard, Norway. The Svalbard samples came from volcanoes that erupted in a freezing Arctic climate about 1 million years ago — possibly mimicking conditions on early Mars.

“Organic material occurs within tiny spheres of carbonate minerals in both the Martian and Earth rocks,â€? said Andrew Steele, lead author of the study. “We found that the organic material is closely associated with the iron oxide mineral magnetite, which is the key to understanding how these compounds formed.”

“The results of this study show that volcanic activity in a freezing climate can produce organic compounds,” said Hans E.F. Amundsen, a co-author in the study from Earth and Planetary Exploration Services. “This implies that building blocks of life can form on cold rocky planets throughout the Universe.”

The organic material in the Allan Hills meteorite may have formed during two different events. The first, similar to the Svalbard samples, was during rapid cooling of fluids on Mars. A second event produced organic material from carbonate minerals during impact ejection of ALH84001 from Mars.

“Our finding sets the stage for the Mars Science Laboratory (MSL) mission in 2009,” said Steele, who is a member of the Sample Analysis on Mars (SAM) instrument team onboard MSL. “We now know that Mars can produce organic compounds. Part of the mission’s goal is to identify organic compounds, their sources, and to detect molecules relevant to life. We know that they are there. We just have to find them.”

This makes the MSL mission all the more exciting and anticipated. And perhaps the team of scientists who made the claims about microbes in ALH 84001 back in 1996 have something to strengthen their case.

Original News Source: Carnegie Institution For Science Press Release

Meteorites Reveal Mars’ Past: Molten Surface, Thick Atmosphere

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If Mars ever had water flowing on its surface, as the many canyons and riverbed-like features on the Red Planet seem to indicate, it also would have needed a thicker atmosphere than what encircles that planet today. New research has revealed that Mars did indeed have a thick atmosphere for about 100 million years after the planet was formed. But the only thing flowing on Mars’ surface at that time was an ocean of molten rock.

A study of Martian meteorites found on Earth shows that Mars had a magma ocean for millions of years, which is surprisingly long, according to Qing-Zhu Yin, assistant professor of geology at the University of California- Davis. For such a persistent event, a thick atmosphere had to blanket Mars to allow the planet to cool slowly.

Meteorites called shergottites were studied to document volcanic activities on Mars between 470 million and 165 million years ago. These rocks were later thrown out of Mars’ gravity field by asteroid impacts and delivered to Earth — a free “sample return mission” as the scientists called it — accomplished by nature.

By precisely measuring the ratios of different isotopes of neodymium and samarium, the researchers could measure the age of the meteorites, and then use them to work out what the crust of Mars was like billions of years before that. Previous estimates for how long the surface remained molten ranged from thousands of years to several hundred million years.

The research was conducted by the Lunar and Planetary Institute, UC Davis and the Johnson Space Center.

Planets form by dust and rocks coming together to form planetisimals, and then these small planets collide together to form larger planets. The giant collisions in this final phase would release huge amounts of energy with nowhere to go except back into the new planet. The rock would turn to molten magma and heavy metals would sink to the core of the planet, releasing additional energy. The molten mantle eventually cools to form a solid crust on the surface.

Although Mars appears to no longer be volcanically active, NASA’s Mars Global Surveyor Spacecraft discovered that the Red Planet hasn’t completely cooled since its formation 4.5 billion years ago. Data from MGS in 2003 indicated that Mars’ core is made either of entirely liquid iron, or it has a solid iron center surrounded by molten iron.

Original News Source: UC Davis Press Release

Building an Antimatter Spaceship

If you’re looking to build a powerful spaceship, nothing’s better than antimatter. It’s lightweight, extremely powerful and could generate tremendous velocity. However, it’s enormously expensive to create, volatile, and releases torrents of destructive gamma rays. NASA’s Institute for Advanced Concepts is funding a team of researchers to try and design an antimatter-powered spacecraft that could avoid some of those problems.

Most self-respecting starships in science fiction stories use anti matter as fuel for a good reason – it’s the most potent fuel known. While tons of chemical fuel are needed to propel a human mission to Mars, just tens of milligrams of antimatter will do (a milligram is about one-thousandth the weight of a piece of the original M&M candy).

However, in reality this power comes with a price. Some antimatter reactions produce blasts of high energy gamma rays. Gamma rays are like X-rays on steroids. They penetrate matter and break apart molecules in cells, so they are not healthy to be around. High-energy gamma rays can also make the engines radioactive by fragmenting atoms of the engine material.

The NASA Institute for Advanced Concepts (NIAC) is funding a team of researchers working on a new design for an antimatter-powered spaceship that avoids this nasty side effect by producing gamma rays with much lower energy.

Antimatter is sometimes called the mirror image of normal matter because while it looks just like ordinary matter, some properties are reversed. For example, normal electrons, the familiar particles that carry electric current in everything from cell phones to plasma TVs, have a negative electric charge. Anti-electrons have a positive charge, so scientists dubbed them “positrons”.

When antimatter meets matter, both annihilate in a flash of energy. This complete conversion to energy is what makes antimatter so powerful. Even the nuclear reactions that power atomic bombs come in a distant second, with only about three percent of their mass converted to energy.

Previous antimatter-powered spaceship designs employed antiprotons, which produce high-energy gamma rays when they annihilate. The new design will use positrons, which make gamma rays with about 400 times less energy.

The NIAC research is a preliminary study to see if the idea is feasible. If it looks promising, and funds are available to successfully develop the technology, a positron-powered spaceship would have a couple advantages over the existing plans for a human mission to Mars, called the Mars Reference Mission.

“The most significant advantage is more safety,” said Dr. Gerald Smith of Positronics Research, LLC, in Santa Fe, New Mexico. The current Reference Mission calls for a nuclear reactor to propel the spaceship to Mars. This is desirable because nuclear propulsion reduces travel time to Mars, increasing safety for the crew by reducing their exposure to cosmic rays. Also, a chemically-powered spacecraft weighs much more and costs a lot more to launch. The reactor also provides ample power for the three-year mission. But nuclear reactors are complex, so more things could potentially go wrong during the mission. “However, the positron reactor offers the same advantages but is relatively simple,” said Smith, lead researcher for the NIAC study.

Also, nuclear reactors are radioactive even after their fuel is used up. After the ship arrives at Mars, Reference Mission plans are to direct the reactor into an orbit that will not encounter Earth for at least a million years, when the residual radiation will be reduced to safe levels. However, there is no leftover radiation in a positron reactor after the fuel is used up, so there is no safety concern if the spent positron reactor should accidentally re-enter Earth’s atmosphere, according to the team.

It will be safer to launch as well. If a rocket carrying a nuclear reactor explodes, it could release radioactive particles into the atmosphere. “Our positron spacecraft would release a flash of gamma-rays if it exploded, but the gamma rays would be gone in an instant. There would be no radioactive particles to drift on the wind. The flash would also be confined to a relatively small area. The danger zone would be about a kilometer (about a half-mile) around the spacecraft. An ordinary large chemically-powered rocket has a danger zone of about the same size, due to the big fireball that would result from its explosion,” said Smith.

Another significant advantage is speed. The Reference Mission spacecraft would take astronauts to Mars in about 180 days. “Our advanced designs, like the gas core and the ablative engine concepts, could take astronauts to Mars in half that time, and perhaps even in as little as 45 days,” said Kirby Meyer, an engineer with Positronics Research on the study.

Advanced engines do this by running hot, which increases their efficiency or “specific impulse” (Isp). Isp is the “miles per gallon” of rocketry: the higher the Isp, the faster you can go before you use up your fuel supply. The best chemical rockets, like NASA’s Space Shuttle main engine, max out at around 450 seconds, which means a pound of fuel will produce a pound of thrust for 450 seconds. A nuclear or positron reactor can make over 900 seconds. The ablative engine, which slowly vaporizes itself to produce thrust, could go as high as 5,000 seconds.

One technical challenge to making a positron spacecraft a reality is the cost to produce the positrons. Because of its spectacular effect on normal matter, there is not a lot of antimatter sitting around. In space, it is created in collisions of high-speed particles called cosmic rays. On Earth, it has to be created in particle accelerators, immense machines that smash atoms together. The machines are normally used to discover how the universe works on a deep, fundamental level, but they can be harnessed as antimatter factories.

“A rough estimate to produce the 10 milligrams of positrons needed for a human Mars mission is about 250 million dollars using technology that is currently under development,” said Smith. This cost might seem high, but it has to be considered against the extra cost to launch a heavier chemical rocket (current launch costs are about $10,000 per pound) or the cost to fuel and make safe a nuclear reactor. “Based on the experience with nuclear technology, it seems reasonable to expect positron production cost to go down with more research,” added Smith.

Another challenge is storing enough positrons in a small space. Because they annihilate normal matter, you can’t just stuff them in a bottle. Instead, they have to be contained with electric and magnetic fields. “We feel confident that with a dedicated research and development program, these challenges can be overcome,” said Smith.

If this is so, perhaps the first humans to reach Mars will arrive in spaceships powered by the same source that fired starships across the universes of our science fiction dreams.

Original Source: NASA News Release