Clearing space debris, the surprising core of Mars and SpaceX's Starship gears up for takeoff. This Week in Space

The Space Debris Legislation – Second Attempt

The U.S. Senate has unanimously passed a bill instructing the United States space agency, NASA, to formulate plans for the removal of space debris from low Earth orbit. According to the proposal, the agency is required to launch a competitive project aimed at selecting a technology for the removal of space debris. The selection of targets for debris removal will be done in cooperation with the U.S. Department of Commerce, which will lead the effort to establish appropriate policies for space traffic regulation. The legislation also tasks the United States National Space Council with overseeing government actions concerning space debris management.

This bill closely resembles a previous bill that was approved by the Senate at the end of 2022 but ultimately failed to pass in the House of Representatives. To become law and undergo signing by the president, a bill must secure approval from both houses of Congress. Presently, Democratic lawmakers are striving to advance the bill through the House of Representatives, hoping that this time it will be approved.

The term "space debris" refers to all artificial objects in orbit around Earth that are neither active satellites nor active spacecraft. Authorities in the United States and various other countries are currently monitoring thousands of debris pieces larger than 10 centimeters, with the number of smaller debris particles likely exceeding one million. These fragments pose significant risks to operational spacecraft and satellites and, with potential collisions, with either active or inactive objects, further exacerbating the debris problem by generating additional fragments.

Although multiple initiatives and ideas have surfaced to address this issue, concrete action and funding have been slow, relying on the commitment of individual nations. The U.S. recently levied its first, largely symbolic, fine against a company that neglected to deorbit a satellite post-mission. Nonetheless, even if generation of new space debris ceased immediately, the existing debris could continue to multiply and pose a threat due to the possibility of collisions, underlining the necessity for substantial financial investment in space debris cleanup initiatives.

Over a million particles orbiting Earth. A simulation depicting the volume of space debris around our planet | Source: IARPA

Embryonic Development in Space

As humanity envisions the prospect of embarking on  long-distance journeys to distant planets and possibly even venturing beyond our solar system, the potential for extended space missions spanning years or even generations presents a significant challenge  – the ability to reproduce and produce offspring in space.  Early animal experiments in this regard have yielded less than promising outcomes. A recent Japanese study, the results of which were published at the end of the previous weekend, offers more encouraging data, although it underscores that the path to safe reproduction under microgravity conditions remains lengthy.

The team from Yamanashi University embarked on an innovative experiment, dispatching to the International Space Station (ISS) mouse embryos at the earliest stage of their development - shortly after the first division of the fertilized egg into two cells. These embryos were cryogenically preserved and housed in a specialized apparatus allowing them to be thawed at the desired time and transferred to a growth medium in an almost automated process, circumventing the need for astronauts skilled in laboratory procedures. Following thawing, the embryos were allowed to develop for four days, which corresponds to approximately a fifth of the mouse gestation period, followed by their preservation with a fixative. A parallel control group on Earth was subjected to the same precise treatment for comparison. On the space station, the embryos were divided into two groups: one was subjected to artificial gravity mimicking Earth's gravity, and the other was left to develop under the microgravity conditions present at the ISS.

The experiment showed that in all three groups there were embryos that developed well, progressing to the blastocyst stage,  a critical phase in embryonic development after which embryonic division into distinct parts begins. However, it's essential to note that the number of embryos that reached this stage was relatively low. Out of 360 embryos in each group, only 17 developed to the blastocyst stage under microgravity conditions (24 percent of the surviving cells), and 19 did so under artificial gravity (31 percent of the surviving cells). In the Earth-based control experiment, 82 embryos reached this stage, which accounted for approximately 61 percent of the surviving cells following freezing and thawing. Notably, the embryos that reached the blastocyst stage appeared normal, and the researchers did not detect more DNA damage in the cells grown in space compared to those in the Earth control group.

"Based on these reports and our results, perhaps mammalian space reproduction is possible, although it may be somewhat affected. Unfortunately, the number of blastocysts obtained from the ISS experiment was not abundant; and we have not been able to confirm the impact on offspring because we have not produced offspring from embryos developed in space," the researchers write. "The study of mammalian reproduction in space is essential to start the space age, making it necessary to study and clarify the effect of space environment before the ISS is no longer operational."

The embryos appear normal, but only a few of them survived in space to the advanced stage of the experiment. Some of the blastocysts that developed under microgravity conditions | Photo from the mentioned research study

The Warm Heart of Mars 

The question of the internal composition of Mars continues to occupy many researchers, among other reasons because it may constitute the key to the question of how the neighboring planet lost its atmosphere and turned from a wet Earth-like environment into the barren desert it is today. Previous research, which was based on data collected by the Mars geology research lander, InSight, found that the planet's core is larger than expected, with a diameter of about 1,800 kilometers, is liquid, and is less dense than a core containing only liquid iron, as was previously thought.

In two recent studies—one by an international team of scientists led by researchers from France and the other by researchers from Switzerland, seismographic measurements from the Mars lander have been reevaluated. The focus of this analysis was on the data collected following a significant meteorite impact on Mars in 2021, which generated robust seismic waves, affording scientists the opportunity to  to track them as they traversed through the planet’s core. The latest findings  align more closely with initial assumptions: the Martian core measures approximately 1,600 kilometers in diameter and has a density consistent with previous expectations. The most intriguing aspect of these findings lies in the discovery of a previously undetected molten rock layer surrounding the core, with a thickness ranging from 150 to 250 kilometers. The presence of this layer could offer an explanation for why earlier measurements had overestimated the core's size while underestimating its density.

The researchers estimate that  what prevents this molten rock layer from cooling and solidifying is the heat emitted from the activity of radioactive elements within it. However, this hypothesis poses a new challenge, as it contradicts the assumption that Mars' historical global magnetic field was driven by the movements that resulted from the cooling and solidification of the core. If a radioactive layer still exists today, maintaining heat, it contradicts the cooling theory. An alternative proposition emerges: Mars might have had larger moons in the past than its present diminutive pair, exerting gravitational forces on the core and creating a dynamo effect responsible for generating magnetism. However, the researchers acknowledge that this is a speculative idea, and so far there is no evidence to support it. It appears that the puzzle of Mars's geological history will continue to occupy researchers for a long time. Although the InSight lander ceased operations at the end of 2022, the wealth of data it collected during its four-year of activity on Mars promises to provide researchers with ample material for many years to come. 

Deep surprises. Mars's core and the radioactive layer of molten rock that surrounds it | Illustration: IPGP-CNES

SpaceX Navigates Regulatory Landscape Ahead of Starship Test Launch

This week, SpaceX has made further progress towards another test launch of the Starship spacecraft: The United States Federal Aviation Administration (FAA) has completed its examination of the company's safety defect corrections in preparation for a renewed launch license for both the Starship and its Super Heavy launch vehicle. The FAA launched an investigation following the previous test in April this year, which ended with a controlled explosion a mere four minutes post-lift-off, due to a malfunction in the separation of the spacecraft from the launch vehicle. The rocket's explosion in the sky led to reports of damage and potential risks to property. Similar concerns arose following the launch itself. In the investigation report, the administration identified 63 defects, 27 of which were related to public safety, and it appears that the company has successfully addressed all of these issues. Among the reported defects were issues with the launch pad, which the company has since rectified, and a malfunction that caused a delay in the spacecraft's controlled detonation, resulting in a lower-altitude explosion with a higher potential for damage.

Despite the FAA's approval of the corrections after examination, SpaceX is still awaiting approval from another regulatory body, the Fish and Wildlife Service (FWS). This approval is essential to ensure that the company has also addressed any defects that could pose risks to wildlife and vegetation near its launch site in Boca Chica, South Texas. Last week, the service announced that it is working with the FAA on a biological report, and although it has 135 days to complete it, it does not anticipate needing the full timeframe. SpaceX's Vice President, Bill Gerstenmaier, recently said that the company has been ready for launch for over a month, waiting only for the approval of the relevant regulatory authorities. “When it comes to projects of national interest, such as the Artemis program, Congress should establish a regulatory regime consistent with the national program’s objectives and schedules,” Gerstenmaier said during a Senate subcommittee discussion on space issues,  referring to Starship's planned role as the lunar lander vehicle in the program's first manned landings, which may be delayed due to the delays in the spacecraft's tests. “Agencies supporting the FAA licensing process, like those with environmental responsibilities, should also be required to complete their work consistent with the national program schedules,” he stated.

Safety check completed, now awaiting environmental clearance. Starship spacecraft and Super Heavy rocket on the launch pad in Boca Chica, Texas | Photo: SpaceX