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Category Archives: 06. The terrestrial planets: Earth, Moon, and their relatives

Adapted from a press release of Mars Odyssey’s THEMIS team, March 5. 2015:

NASA’s next Mars space probe, a lander named InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport), is due to touch down on the Red Planet in September 2016. InSight carries two main instruments, a heat-flow probe and a seismometer, both being deployed using a robotic arm. The heat probe requires that the ground within reach of the arm be penetrable by the probe, which will hammer itself into the soil to a depth of three to five meters.


Credit: NASA/JPL

InSight was provisionally selected for funding through NASA’s Discovery Program for launch in 2016 and the spacecraft design is based on NASA’s successful Phoenix Mars lander mission. It will touch down in one place and stay there for its entire mission, projected to last two Earth years. Its landing place has been chosen carefully with help from a Mars-orbiting heat-sensitive camera on NASA’s Mars Odyssey orbiter.

Links: THEMIS press release, ASU press release, InSight mission home.



The European Space Agency’s ExoMars mission is set for launch in 2018.  A rover and a lander are included, to search for evidence of past and present life on Mars. The orbiter, part of the ExoMars 2016 mission, will sample the Martian atmospheric trace gases, such as methane and provide communications. The rover will leave the landing platform and drill into the surface to search for potential fossils, relevant minerals, and organic molecules (with chirality as biomarkers).


Credit: ESA

In addition to its scientific exploration, the mission will help test in-situ technologies that might pave the way for a future international Mars sample return mission.

Links: ExoMars 2018 mission overview; ESA Mars homepage.

Adapted from an NOAA press release, February 11, 2015:

On February 11, the United States Air Force launched a National Oceanic and Atmospheric Administration (NOAA) satellite called Deep Space Climate Observatory, or DSCOVR, into orbit. NOAA will use DSCOVR to monitor the solar wind and forecast space weather at Earth — effects from the material and energy from the Sun that can impact our satellites and technological infrastructure on Earth.

Data from DSCOVR, coupled with a new forecast model, will enable NOAA forecasters to predict geomagnetic storm magnitude on a regional basis. Geomagnetic storms occur when plasma and magnetic fields streaming from the Sun impact Earth’s magnetic field. Large magnetic eruptions from the sun have the potential to bring major disruptions to power grids, aviation, telecommunications, and GPS systems.


The DSCOVR mission is a partnership between NOAA, NASA, and the U.S. Air Force.

In addition to space weather-monitoring instruments, DSCOVR is carrying two NASA Earth-observing instruments that will gather a range of measurements from ozone and aerosol amounts, to changes in Earth’s radiation.

Links: original NOAA press release; NY Times article about the launch, DSCOVR home.

From an article on CNET by Michelle Starr, February 12, 2015; visualizations by Ernie Wright:

As the Moon orbits the Earth, we only ever see the one side. This is because the moon is tidally locked – a single rotation of its axis takes the same amount of time as a single orbit around the Earth, so that the same side is always facing the Earth. Using its Lunar Reconnaissance Orbiter, NASA has collated data to reveal what the other side of the Moon looks like (see Section 6.2a, p. 127 and Figure 6-18, p. 133).


Credit: NASA’s Goddard SFC Scientific Visualization Studio

As the Moon goes through its phases, we see it darken and lighten as viewed from Earth. Those phases are the opposite of what the far side of the Moon experiences: when we have a Full Moon, the far side is new; when we have a New Moon, the far side is full. This means that the LRO can observe the far side of the Moon in pretty good detail when it is illuminated by the Sun.

In the years since it launched in 2009, the LRO has sent back hundreds of terabytes of data about the Moon’s far side. What it has found is that the far side of the Moon is quite different from the side we see.

Links: CNET article; more information from NASA’s Scientific Visualization Studio; LRO home.

Abridged from a New Scientist article by Rebecca Boyle, September 30, 2014:

A newly discovered asteroid called 2014 OL339 is the latest quasi-satellite of Earth – a space rock that orbits the Sun but is close enough to Earth to look like a companion. The asteroid has been hanging out near Earth for about 775 years, but its orbit is unstable – it will probably move on about 165 years from now.

Credit: NASA

Credit: NASA

Quasi-satellites orbit in resonance with Earth, allowing our planet’s gravity to shift the rock’s position. The asteroid orbits the Sun every 365 days, as Earth does, but Earth’s gravity guides it into an eccentric wobble, which causes the rock to appear to circle backward around the planet.

The asteroid, which is between 90 and 200 metres in diameter, is among several different categories of space rock in Earth’s retinue besides our one satellite, the Moon. Rocks that hang out at a gravitational middle ground known as a Lagrange point, where they follow or lead Earth in its orbit, are called Trojans.

Links: The full New Scientist article; NASA’s Near-Earth Object program.

An uncrewed Chinese lunar probe was launched on October 23, 2014, to fly around the Moon and back to Earth, in an 8-day mission. Called Chang’e 5-T1, it was a test mission in advance of the Chinese 2017 Chang’e 5 mission that is planned to return lunar rocks and soil to Earth. The return capsule of Chang’e 5-T1 landed in Inner Mongolia, on October 31, 2014.
Chang'e 5T1


Like its predecessors, the spacecraft is named after the Chinese Moon goddess Chang’e.
Links: report on
Astronomy Picture of the Day (APOD) for November 1, 2014, shows Mars the day after Comet Siding Spring’s close encounter, with the comet visible at the edge of its overexposed disk.

Credit & copyright: Rolando Ligustri (CARA Project, CAST)

The caption describes: “this comet [came] within 86,700 miles or so of Mars, about one-third the Earth-Moon distance. Earth’s spacecraft and rovers in Mars orbit and on the surface reported no ill effects though, and had a ringside seat as a visitor from the outer Solar System passed by.”
Credit: USGS

Credit: USGS

Scientists at the U.S. Geological Survey (USGS) have released a new global geologic map of Mars, which records the distribution of geologic units and landforms on the planet’s surface through time. It is based on the unprecedented variety, quality, and quantity of remotely sensed data acquired since the Viking Orbiters. These data have provided morphologic, topographic, spectral, thermophysical, radar sounding, and other observations for integration, analysis, and interpretation in support of geologic mapping. In particular, the precise topographic mapping now available through laser altimetry has enabled a consistent portrayal of the surface for global mapping. Also, they use thermal infrared image bases, which tend to be less affected by atmospheric haze and are reliable for analysis of surface morphology and texture at even higher resolutions.

Links: USGS Map 3292 hompeage with further resources, PDF with detailed key (file is 35 MB), external link to movie of rotating geologic surface of Mars (Credit: Jennifer LaVista/USGS), NY Times article describing the new map, Eos article by Ken Tanaka (link to PDF).

From a European Space Agency (ESA) press release, May 16. 2014:

After eight years in orbit, ESA’s Venus Express orbiting mission has completed routine science observations and is preparing for a daring plunge into the planet’s hostile atmosphere. Its suite of seven instruments have provided a comprehensive study of the ionosphere, atmosphere and surface of Venus.

Credit: ESA, C. Carreau

Credit: ESA, C. Carreau

The spacecraft’s fuel supplies, necessary to maintain its elliptical orbit, are running low and will soon be exhausted. The routine science operations concluded this week and the spacecraft is being prepared for one final mission: to make a controlled plunge deeper into the atmosphere than ever before attempted.

This experimental ‘aerobraking’ phase is planned for June 18 – July 11, during which time some limited science measurements with the spacecraft’s magnetic field, solar wind and atom analyzing instruments will be possible. Also, temperature and pressure sensors will record the conditions that the spacecraft experiences.

It is possible that the remaining fuel in Venus Express will be exhausted during this phase or that the spacecraft does not survive these risky operations. But if the spacecraft is still healthy afterwards, its orbit will be raised again and limited operations will continue for several more months, fuel permitting. However, by the end of the year, it is likely that Venus Express will have made its final descent into the atmosphere of the planet, bringing a fantastic scientific endeavor to an end.

Links: ESA press release; link to aerobraking movie (approx 1 min 30 s).



From a NASA press release, April 18, 2014:

Ground controllers at NASA’s Ames Research Center in Moffett Field, California, have confirmed that NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft impacted the surface of the Moon, as planned, on Thursday, April 17. LADEE lacked fuel to maintain a long-term lunar orbit or continue science operations and was intentionally sent into the lunar surface. The spacecraft’s orbit naturally decayed following the mission’s final low-altitude science phase. (See p. 135.)

Credit: NASA

During impact, engineers believe the LADEE spacecraft, the size of a vending machine, broke apart, with most of the spacecraft’s material heating up several hundred degrees – or even vaporizing – at the surface. Any material that remained is likely buried in shallow craters. At the time of impact, LADEE was traveling at a speed of 3,600 miles per hour.

In early April, the spacecraft was commanded to carry out maneuvers that would lower its closest approach to the lunar surface. The new orbit brought LADEE to altitudes below one mile (two kilometers) above the lunar surface. This is lower than most commercial airliners fly above Earth, enabling scientists to gather unprecedented science measurements.

In the coming months, mission controllers will determine the exact time and location of LADEE’s impact and work with the agency’s Lunar Reconnaissance Orbiter (LRO) team to possibly capture an image of the impact site. A thorough understanding of the characteristics of our nearest celestial neighbor will help researchers understand other bodies in the solar system, such as large asteroids, Mercury and the moons of outer planets.

Links: full NASA press release; NY Times article; LADEE mission homepage.